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+Function Compare-WorkSheet {
+<#
+    .Synopsis 
+        Compares two worksheets with the same name in different files. 
+    .Description
+        This command takes two file names, a worksheet name and a name for a key column. 
+        It reads the worksheet from each file and decides the column names.
+        It builds as hashtable of the key column values and the rows they appear in  
+        It then uses PowerShell's compare object command to compare the sheets (explicity checking all column names which have not been excluded)
+        For the difference rows it adds the row number for the key of that row - we have to add the key after doing the comparison, 
+        otherwise rows will be considered as different simply because they have different row numbers 
+        We also add the name of the file in which the difference occurs.  
+        If -BackgroundColor is specified the difference rows will be changed to that background. 
+    .Example 
+        Compare-WorkSheet -Referencefile 'Server56.xlsx' -Differencefile 'Server57.xlsx'  -WorkSheetName Products -key IdentifyingNumber -ExcludeProperty Install* | format-table
+        The two workbooks in this example contain the result of redirecting a subset of properties from Get-WmiObject -Class win32_product to Export-Excel
+        The command compares the "products" pages in the two workbooks, but we don't want to register a differnce if if the software was installed on a 
+        different date or from a different place,  so Excluding Install* removes InstallDate and InstallSource. 
+        This data doesn't have a "name" column" so we specify the "IdentifyingNumber" column as the key.  
+        The results will be presented as a table.  
+    .Example 
+        compare-WorkSheet "Server54.xlsx" "Server55.xlsx" -WorkSheetName services -GridView  
+        This time two workbooks contain the result of redirecting Get-WmiObject -Class win32_service to Export-Excel 
+        Here the -Differencefile and -Referencefile parameter switches are assumed  , and the default setting for -key ("Name") works for services
+        This will display the differences between the "services" sheets using a grid view 
+    .Example 
+        Compare-WorkSheet  'Server54.xlsx' 'Server55.xlsx'  -WorkSheetName Services -BackgroundColor lightGreen
+        This version of the command outputs the differences between the "services" pages and also highlights any different rows in the spreadsheet files. 
+    .Example 
+        Compare-WorkSheet 'Server54.xlsx' 'Server55.xlsx'  -WorkSheetName Services -BackgroundColor lightGreen -FontColor Red -Show
+        This builds on the previous example: this time Where two changed rows have the value in the "name" column (the default value for -key),
+        this version adds highlighting of the changed cells in red; and then opens the Excel file.
+    .Example
+        Compare-WorkSheet 'Pester-tests.xlsx' 'Pester-tests.xlsx' -WorkSheetName 'Server1','Server2' -Property "full Description","Executed","Result" -Key "full Description"
+        This time the reference file and the difference file are the same file and two different sheets are used. Because the tests include the
+        machine name and time the test was run the command specifies a limited set of columns should be used.    
+    .Example
+        Compare-WorkSheet  'Server54.xlsx' 'Server55.xlsx' -WorkSheetName general -Startrow 2 -Headername Label,value -Key Label -GridView -ExcludeDifferent 
+        The "General" page has a title and two unlabelled columns with a row forCPU, Memory, Domain, Disk and so on 
+        So the command is instructed to starts at row 2 to skip the title and to name the columns: the first is "label" and the Second "Value";
+         the label acts as the key. This time we interested the rows which are the same in both sheets, 
+        and the result is displayed using grid view. Note that grid view works best when the number of columns is small. 
+    .Example
+        Compare-WorkSheet 'Server1.xlsx' 'Server2.xlsx' -WorkSheetName general -Startrow 2 -Headername Label,value -Key Label -BackgroundColor White -Show -AllDataBackgroundColor LightGray
+        This version of the previous command lightlights all the cells in lightgray and then sets the changed rows back to white; only 
+        the unchanged rows are highlighted
+#>
+    [cmdletbinding(DefaultParameterSetName)]
+    Param(
+        #First file to compare 
+        [parameter(Mandatory=$true,Position=0)]
+        $Referencefile ,
+        #Second file to compare
+        [parameter(Mandatory=$true,Position=1)]
+        $Differencefile   ,
+        #Name(s) of worksheets to compare.
+        $WorkSheetName   = "Sheet1",
+        #Properties to include in the DIFF - supports wildcards, default is "*"
+        $Property        = "*"    ,
+        #Properties to exclude from the the search - supports wildcards 
+        $ExcludeProperty ,
+        #Specifies custom property names to use, instead of the values defined in the column headers of the TopRow.
+        [Parameter(ParameterSetName='B', Mandatory)]
+        [String[]]$Headername,   
+        #Automatically generate property names (P1, P2, P3, ..) instead of the using the values the top row of the sheet
+        [Parameter(ParameterSetName='C', Mandatory)]
+        [switch]$NoHeader, 
+        #The row from where we start to import data, all rows above the StartRow are disregarded. By default this is the first row.
+        [int]$Startrow = 1, 
+        #If specified, highlights all the cells - so you can make Equal cells one colour, and Diff cells another. 
+        [System.Drawing.Color]$AllDataBackgroundColor,
+        #If specified, highlights the DIFF rows 
+        [System.Drawing.Color]$BackgroundColor,
+        #If specified identifies the tabs which contain DIFF rows  (ignored if -backgroundColor is omitted)   
+        [System.Drawing.Color]$TabColor,
+        #Name of a column which is unique and will be used to add a row to the DIFF object, default is "Name" 
+        $Key             = "Name" ,
+        #If specified, highlights the DIFF columns in rows which have the same key.  
+        [System.Drawing.Color]$FontColor,
+        #If specified opens the Excel workbooks instead of outputting the diff to the console (unless -passthru is also specified) 
+        [Switch]$Show,
+        #If specified, the command tries to the show the DIFF in a Gridview and not on the console. (unless-Passthru is also specified). This Works best with few columns selected, and requires a key 
+        [switch]$GridView,
+        #If specified -Passthrough full set of diff data is returned without filtering to the specified properties 
+        [Switch]$PassThru,
+        #If specified the result will include equal rows as well. By default only different rows are returned 
+        [Switch]$IncludeEqual,
+        #If Specified the result includes only the rows where both are equal
+        [Switch]$ExcludeDifferent
+    )
+    
+    #if the filenames don't resolve, give up now. 
+    try    { $oneFile = ((Resolve-Path -Path $Referencefile -ErrorAction Stop).path -eq (Resolve-Path -Path $Differencefile  -ErrorAction Stop).path)}
+    Catch  { Write-Warning -Message "Could not Resolve the filenames." ; return } 
+        
+    #If we have one file , we mush have two different worksheet names. If we have two files we can a single string or two strings. 
+    if     ($onefile -and ( ($WorkSheetName.count -ne 2) -or $WorkSheetName[0] -eq $WorkSheetName[1] ) ) {
+        Write-Warning -Message "If both the Reference and difference file are the same then worksheet name must provide 2 different names" 
+        return
+    }
+    if     ($WorkSheetName.count -eq 2)       {$worksheet1 = $WorkSheetName[0] ;   $WorkSheet2 = $WorkSheetName[1]} 
+    elseif ($WorkSheetName -is [string])      {$worksheet1 = $WorkSheet2 = $WorkSheetName}
+    else   {Write-Warning -Message "You must provide either a single worksheet name or two names." ; return }   
+    
+    $params= @{ ErrorAction = [System.Management.Automation.ActionPreference]::Stop } 
+    foreach ($p in @("HeaderName","NoHeader","StartRow")) {if ($PSBoundParameters[$p]) {$params[$p] = $PSBoundParameters[$p]}}
+    try    {
+        $Sheet1 = Import-Excel -Path $Referencefile  -WorksheetName $WorkSheet1 @params                                                                       
+        $Sheet2 = Import-Excel -Path $Differencefile -WorksheetName $WorkSheet2 @Params 
+    }
+    Catch  {Write-Warning -Message "Could not read the worksheet from $Referencefile and/or $Differencefile." ; return } 
+    
+    #Get Column headings and create a hash table of Name to column letter. 
+    $headings = $Sheet1[-1].psobject.Properties.name # This preserves the sequence - using get-member would sort them alphabetically!
+    $headings | ForEach-Object -Begin {$columns  = @{}  ; $i=65 } -Process  {$Columns[$_] = [char]($i ++) }
+    
+    #Make a list of property headings using the Property (default "*") and ExcludeProperty parameters 
+    if ($Key -eq "Name" -and $NoHeader) {$key  = "p1"} 
+    $propList = @() 
+    foreach ($p in $Property)           {$propList += ($headings.where({$_ -like    $p}) )} 
+    foreach ($p in $ExcludeProperty)    {$propList  =  $propList.where({$_ -notlike $p})  } 
+    if (($headings -contains $key) -and ($propList -notcontains $Key)) {$propList += $Key}
+    $propList = $propList | Select-Object -Unique 
+    if ($propList.Count -eq 0)  {Write-Warning -Message "No Columns are selected with -Property = '$Property' and -excludeProperty = '$ExcludeProperty'." ; return}
+
+    #Add RowNumber, Sheetname and file name to every row 
+    $FirstDataRow = $startRow + 1
+    if ($Headername -or $NoHeader) {$FirstDataRow -- } 
+    $i = $FirstDataRow ; foreach ($row in $Sheet1) {Add-Member -InputObject $row -MemberType NoteProperty -Name "_Row"   -Value ($i ++) 
+                                                    Add-Member -InputObject $row -MemberType NoteProperty -Name "_Sheet" -Value  $worksheet1
+                                                    Add-Member -InputObject $row -MemberType NoteProperty -Name "_File"  -Value  $Referencefile} 
+    $i = $FirstDataRow ; foreach ($row in $Sheet2) {Add-Member -InputObject $row -MemberType NoteProperty -Name "_Row"   -Value ($i ++) 
+                                                    Add-Member -InputObject $row -MemberType NoteProperty -Name "_Sheet" -Value  $worksheet2
+                                                    Add-Member -InputObject $row -MemberType NoteProperty -Name "_File"  -Value  $Differencefile} 
+    
+    if ($ExcludeDifferent -and -not $IncludeEqual) {$IncludeEqual = $true} 
+    #Do the comparison and add file,sheet and row to the result - these are prefixed with "_" to show they are added the addition will fail if the sheet has these properties so split the operations 
+    [PSCustomObject[]]$diff = Compare-Object -ReferenceObject $Sheet1 -DifferenceObject $Sheet2 -Property $propList -PassThru -IncludeEqual:$IncludeEqual -ExcludeDifferent:$ExcludeDifferent  |
+                Sort-Object -Property "_Row","File"
+    
+    #if BackgroundColor was specified, set it on extra or extra or changed rows  
+    if      ($diff -and $BackgroundColor) {
+        #Differences may only exist in one file. So gather the changes for each file; open the file, update each impacted row in the shee, save the file  
+        $updates = $diff.where({$_.SideIndicator -ne "=="}) | Group-object -Property "_File"
+        foreach   ($file in $updates) {
+            try   {$xl  = Open-ExcelPackage -Path $file.name }
+            catch {Write-warning -Message "Can't open $($file.Name) for writing." ; return} 
+            if ($AllDataBackgroundColor) {
+                $file.Group._sheet | Sort-Object -Unique | ForEach-Object {
+                    $ws =  $xl.Workbook.Worksheets[$_] 
+                    if ($headerName) {$range = "A" +  $startrow      + ":" + $ws.dimension.end.address}
+                    else             {$range = "A" + ($startrow + 1) + ":" + $ws.dimension.end.address}
+                    Set-Format -WorkSheet $ws -BackgroundColor $AllDataBackgroundColor -Range $Range 
+                }
+            }
+            foreach ($row in $file.group)  {
+                $ws    = $xl.Workbook.Worksheets[$row._Sheet]
+                $range = $ws.Dimension -replace "\d+",$row._row
+                Set-Format -WorkSheet $ws -Range $range -BackgroundColor $BackgroundColor         
+            }
+            if ($TabColor) {
+                foreach ($tab in ($file.group._sheet | Select-Object -Unique)) {
+                    $xl.Workbook.Worksheets[$tab].TabColor = $TabColor
+                 }
+            }
+            $xl.save()  ; $xl.Stream.Close() ; $xl.Dispose()
+        }
+    }
+    #if font colour was specified, set it on changed properties where the same key appears in both sheets. 
+    if      ($diff -and $FontColor -and ($propList -contains $Key)  ) {
+        $updates = $diff.where({$_.SideIndicator -ne "=="})  | Group-object -Property $Key | Where-Object {$_.count -eq 2} 
+        if ($updates) {
+            $XL1 = Open-ExcelPackage -path $Referencefile
+            if ($oneFile ) {$xl2 = $xl1} 
+            else           {$xl2 = Open-ExcelPackage -path $Differencefile }
+            foreach ($u in $updates) {
+                 foreach ($p in $propList) {
+                    if ($u.group[0]._file -eq $Referencefile) {
+                        $ws1 =  $xl1.Workbook.Worksheets[$u.Group[0]._sheet]
+                        $ws2 =  $xl2.Workbook.Worksheets[$u.Group[1]._sheet]
+                    }
+                    else {
+                        $ws1 =  $xl2.Workbook.Worksheets[$u.Group[0]._sheet]
+                        $ws2 =  $xl1.Workbook.Worksheets[$u.Group[1]._sheet]
+                    }
+                    if($u.Group[0].$p -ne $u.Group[1].$p ) {
+                        Set-Format -WorkSheet $ws1 -Range ($Columns[$p] + $u.Group[0]._Row) -FontColor $FontColor
+                        Set-Format -WorkSheet $ws1 -Range ($Columns[$p] + $u.Group[1]._Row) -FontColor $FontColor
+                    } 
+                } 
+            }
+            $xl1.Save()                     ; $xl1.Stream.Close() ; $xl1.Dispose()
+            if (-not $oneFile) {$xl2.Save() ; $xl2.Stream.Close() ; $xl2.Dispose()}
+        }
+    }
+    elseif  ($diff -and $FontColor) {Write-Warning -Message "To match rows to set changed cells, you must specify -Key and it must match one of the included properties." }   
+
+    #if nothing was found write a message which wont be redirected
+    if (-not $diff) {Write-Host "Comparison of $Referencefile::$worksheet1 and $Differencefile::$WorkSheet2 returned no results."  }
+
+    if      ($show)               { 
+        Start-Process -FilePath $Referencefile 
+        if  (-not $oneFile)  { Start-Process -FilePath $Differencefile }
+        if  ($GridView)      { Write-Warning -Message "-GridView is ignored when -Show is specified" } 
+    }    
+    elseif  ($GridView -and $propList -contains $key) { 
+             
+             
+             if ($IncludeEqual -and -not $ExcludeDifferent) {
+                $GroupedRows = $diff | Group-Object -Property $key  
+             }
+             else { #to get the right now numbers on the grid we need to have all the rows. 
+                $GroupedRows = Compare-Object -ReferenceObject $Sheet1 -DifferenceObject $Sheet2 -Property $propList -PassThru -IncludeEqual  | 
+                                        Group-Object -Property $key                       
+             }
+             #Additions, deletions and unchanged rows will give a group of 1; changes will give a group of 2 .
+
+             #If one sheet has extra rows we can get a single "==" result from compare, but with the row from the reference sheet 
+             #but the row in the other sheet might so we will look up the row number from the key field build a hash table for that  
+             $Sheet2 | ForEach-Object -Begin {$Rowhash = @{} } -Process {$Rowhash[$_.$key] = $_._row } 
+
+             $ExpandedDiff = ForEach ($g in $GroupedRows)  {
+                #we're going to create a custom object from a hash table. We want the fields to be ordered
+                $hash = [ordered]@{}  
+                foreach ($result IN $g.Group) {
+                    # if result indicates equal or "in Reference" set the reference side row. If we did that on a previous result keep it. Otherwise set to "blank"
+                    if     ($result.sideindicator -ne "=>")      {$hash["<Row"] = $result._Row  } 
+                    elseif (-not $hash["<Row"])                  {$hash["<Row"] = "" }
+                    #if we have already set the side, this is the second record, so set side to indicate "changed"     
+                    if     ($hash.Side) {$hash.side = "<>"} else {$hash["Side"] = $result.sideindicator}
+                    #if result is "in reference" and we don't have a matching "in difference" (meaning a change) the lookup will be blank. Which we want.   
+                    $hash[">Row"] = $Rowhash[$g.Name] 
+                    #position the key as the next field (only appears once) 
+                    $Hash[$key]    = $g.Name  
+                    #For all the other fields we care about create <=FieldName and/or =>FieldName 
+                    foreach ($p in $propList.Where({$_ -ne $key})) {
+                        if  ($result.SideIndicator -eq "==")  {$hash[("=>$P")] = $hash[("<=$P")] =$result.$P}
+                        else                                  {$hash[($result.SideIndicator+$P)] =$result.$P}
+                    }
+                } 
+                [Pscustomobject]$hash
+             }
+
+             #Sort by reference row number, and fill in any blanks in the difference-row column
+             $ExpandedDiff = $ExpandedDiff | Sort-Object -Property "<row"  
+             for ($i = 1; $i -lt $ExpandedDiff.Count; $i++) {if (-not $ExpandedDiff[$i].">row") {$ExpandedDiff[$i].">row" = $ExpandedDiff[$i-1].">row" } }   
+             #Sort by difference row number, and fill in any blanks in the reference-row column
+             $ExpandedDiff = $ExpandedDiff | Sort-Object -Property ">row"  
+             for ($i = 1; $i -lt $ExpandedDiff.Count; $i++) {if (-not $ExpandedDiff[$i]."<row") {$ExpandedDiff[$i]."<row" = $ExpandedDiff[$i-1]."<row" } }  
+             
+             #if we had to put the equal rows back, take them out; sort, make sure all the columns are present in row 1 so the grid puts them in, and output              
+             if ( $ExcludeDifferent) {$ExpandedDiff = $ExpandedDiff.where({$_.side -eq "=="}) | Sort-Object -Property "<row" ,">row"  } 
+             elseif ( $IncludeEqual) {$ExpandedDiff = $ExpandedDiff                           | Sort-Object -Property "<row" ,">row"  }
+             else                    {$ExpandedDiff = $ExpandedDiff.where({$_.side -ne "=="}) | Sort-Object -Property "<row" ,">row"  } 
+             $ExpandedDiff | Update-FirstObjectProperties | Out-GridView -Title "Comparing $Referencefile::$worksheet1 (<=) with $Differencefile::$WorkSheet2 (=>)"   
+    }
+    elseif  ($GridView     )  {Write-Warning -Message "To use -GridView you must specify -Key and it must match one of the included properties."  }   
+    elseif  (-not $PassThru)  {return ($diff | Select-Object -Property (@(@{n="_Side";e={$_.SideIndicator}},"_File" ,"_Sheet","_Row") + $propList))}
+    if      (     $PassThru)  {return  $diff }
+}
+=======
+Function Compare-WorkSheet {
+<#
+    .Synopsis 
+        Compares two worksheets with the same name in different files. 
+    .Description
+        This command takes two file names, a worksheet name and a name for a key column. 
+        It reads the worksheet from each file and decides the column names.
+        It builds as hashtable of the key column values and the rows they appear in  
+        It then uses PowerShell's compare object command to compare the sheets (explicity checking all column names which have not been excluded)
+        For the difference rows it adds the row number for the key of that row - we have to add the key after doing the comparison, 
+        otherwise rows will be considered as different simply because they have different row numbers 
+        We also add the name of the file in which the difference occurs.  
+        If -BackgroundColor is specified the difference rows will be changed to that background. 
+    .Example 
+        Compare-WorkSheet -Referencefile 'Server56.xlsx' -Differencefile 'Server57.xlsx'  -WorkSheetName Products -key IdentifyingNumber -ExcludeProperty Install* | format-table
+        The two workbooks in this example contain the result of redirecting a subset of properties from Get-WmiObject -Class win32_product to Export-Excel
+        The command compares the "products" pages in the two workbooks, but we don't want to register a differnce if if the software was installed on a 
+        different date or from a different place,  so Excluding Install* removes InstallDate and InstallSource. 
+        This data doesn't have a "name" column" so we specify the "IdentifyingNumber" column as the key.  
+        The results will be presented as a table.  
+    .Example 
+        compare-WorkSheet "Server54.xlsx" "Server55.xlsx" -WorkSheetName services -GridView  
+        This time two workbooks contain the result of redirecting Get-WmiObject -Class win32_service to Export-Excel 
+        Here the -Differencefile and -Referencefile parameter switches are assumed  , and the default setting for -key ("Name") works for services
+        This will display the differences between the "services" sheets using a grid view 
+    .Example 
+        Compare-WorkSheet  'Server54.xlsx' 'Server55.xlsx'  -WorkSheetName Services -BackgroundColor lightGreen
+        This version of the command outputs the differences between the "services" pages and also highlights any different rows in the spreadsheet files. 
+    .Example 
+        Compare-WorkSheet 'Server54.xlsx' 'Server55.xlsx'  -WorkSheetName Services -BackgroundColor lightGreen -FontColor Red -Show
+        This builds on the previous example: this time Where two changed rows have the value in the "name" column (the default value for -key),
+        this version adds highlighting of the changed cells in red; and then opens the Excel file.
+    .Example
+        Compare-WorkSheet 'Pester-tests.xlsx' 'Pester-tests.xlsx' -WorkSheetName 'Server1','Server2' -Property "full Description","Executed","Result" -Key "full Description"
+        This time the reference file and the difference file are the same file and two different sheets are used. Because the tests include the
+        machine name and time the test was run the command specifies a limited set of columns should be used.    
+    .Example
+        Compare-WorkSheet  'Server54.xlsx' 'Server55.xlsx' -WorkSheetName general -Startrow 2 -Headername Label,value -Key Label -GridView -ExcludeDifferent 
+        The "General" page has a title and two unlabelled columns with a row forCPU, Memory, Domain, Disk and so on 
+        So the command is instructed to starts at row 2 to skip the title and to name the columns: the first is "label" and the Second "Value";
+         the label acts as the key. This time we interested the rows which are the same in both sheets, 
+        and the result is displayed using grid view. Note that grid view works best when the number of columns is small. 
+    .Example
+        Compare-WorkSheet 'Server1.xlsx' 'Server2.xlsx' -WorkSheetName general -Startrow 2 -Headername Label,value -Key Label -BackgroundColor White -Show -AllDataBackgroundColor LightGray
+        This version of the previous command lightlights all the cells in lightgray and then sets the changed rows back to white; only 
+        the unchanged rows are highlighted
+#>
+    [cmdletbinding(DefaultParameterSetName)]
+    Param(
+        #First file to compare 
+        [parameter(Mandatory=$true,Position=0)]
+        $Referencefile ,
+        #Second file to compare
+        [parameter(Mandatory=$true,Position=1)]
+        $Differencefile   ,
+        #Name(s) of worksheets to compare.
+        $WorkSheetName   = "Sheet1",
+        #Properties to include in the DIFF - supports wildcards, default is "*"
+        $Property        = "*"    ,
+        #Properties to exclude from the the search - supports wildcards 
+        $ExcludeProperty ,
+        #Specifies custom property names to use, instead of the values defined in the column headers of the TopRow.
+        [Parameter(ParameterSetName='B', Mandatory)]
+        [String[]]$Headername,   
+        #Automatically generate property names (P1, P2, P3, ..) instead of the using the values the top row of the sheet
+        [Parameter(ParameterSetName='C', Mandatory)]
+        [switch]$NoHeader, 
+        #The row from where we start to import data, all rows above the StartRow are disregarded. By default this is the first row.
+        [int]$Startrow = 1, 
+        #If specified, highlights all the cells - so you can make Equal cells one colour, and Diff cells another. 
+        [System.Drawing.Color]$AllDataBackgroundColor,
+        #If specified, highlights the DIFF rows 
+        [System.Drawing.Color]$BackgroundColor,
+        #If specified identifies the tabs which contain DIFF rows  (ignored if -backgroundColor is omitted)   
+        [System.Drawing.Color]$TabColor,
+        #Name of a column which is unique and will be used to add a row to the DIFF object, default is "Name" 
+        $Key             = "Name" ,
+        #If specified, highlights the DIFF columns in rows which have the same key.  
+        [System.Drawing.Color]$FontColor,
+        #If specified opens the Excel workbooks instead of outputting the diff to the console (unless -passthru is also specified) 
+        [Switch]$Show,
+        #If specified, the command tries to the show the DIFF in a Gridview and not on the console. (unless-Passthru is also specified). This Works best with few columns selected, and requires a key 
+        [switch]$GridView,
+        #If specified -Passthrough full set of diff data is returned without filtering to the specified properties 
+        [Switch]$PassThru,
+        #If specified the result will include equal rows as well. By default only different rows are returned 
+        [Switch]$IncludeEqual,
+        #If Specified the result includes only the rows where both are equal
+        [Switch]$ExcludeDifferent
+    )
+    
+    #if the filenames don't resolve, give up now. 
+    try    { $oneFile = ((Resolve-Path -Path $Referencefile -ErrorAction Stop).path -eq (Resolve-Path -Path $Differencefile  -ErrorAction Stop).path)}
+    Catch  { Write-Warning -Message "Could not Resolve the filenames." ; return } 
+        
+    #If we have one file , we mush have two different worksheet names. If we have two files we can a single string or two strings. 
+    if     ($onefile -and ( ($WorkSheetName.count -ne 2) -or $WorkSheetName[0] -eq $WorkSheetName[1] ) ) {
+        Write-Warning -Message "If both the Reference and difference file are the same then worksheet name must provide 2 different names" 
+        return
+    }
+    if     ($WorkSheetName.count -eq 2)       {$worksheet1 = $WorkSheetName[0] ;   $WorkSheet2 = $WorkSheetName[1]} 
+    elseif ($WorkSheetName -is [string])      {$worksheet1 = $WorkSheet2 = $WorkSheetName}
+    else   {Write-Warning -Message "You must provide either a single worksheet name or two names." ; return }   
+    
+    $params= @{ ErrorAction = [System.Management.Automation.ActionPreference]::Stop } 
+    foreach ($p in @("HeaderName","NoHeader","StartRow")) {if ($PSBoundParameters[$p]) {$params[$p] = $PSBoundParameters[$p]}}
+    try    {
+        $Sheet1 = Import-Excel -Path $Referencefile  -WorksheetName $WorkSheet1 @params                                                                       
+        $Sheet2 = Import-Excel -Path $Differencefile -WorksheetName $WorkSheet2 @Params 
+    }
+    Catch  {Write-Warning -Message "Could not read the worksheet from $Referencefile and/or $Differencefile." ; return } 
+    
+    #Get Column headings and create a hash table of Name to column letter. 
+    $headings = $Sheet1[-1].psobject.Properties.name # This preserves the sequence - using get-member would sort them alphabetically!
+    $headings | ForEach-Object -Begin {$columns  = @{}  ; $i=65 } -Process  {$Columns[$_] = [char]($i ++) }
+    
+    #Make a list of property headings using the Property (default "*") and ExcludeProperty parameters 
+    if ($Key -eq "Name" -and $NoHeader) {$key  = "p1"} 
+    $propList = @() 
+    foreach ($p in $Property)           {$propList += ($headings.where({$_ -like    $p}) )} 
+    foreach ($p in $ExcludeProperty)    {$propList  =  $propList.where({$_ -notlike $p})  } 
+    if (($headings -contains $key) -and ($propList -notcontains $Key)) {$propList += $Key}
+    $propList = $propList | Select-Object -Unique 
+    if ($propList.Count -eq 0)  {Write-Warning -Message "No Columns are selected with -Property = '$Property' and -excludeProperty = '$ExcludeProperty'." ; return}
+
+    #Add RowNumber, Sheetname and file name to every row 
+    $FirstDataRow = $startRow + 1
+    if ($Headername -or $NoHeader) {$FirstDataRow -- } 
+    $i = $FirstDataRow ; foreach ($row in $Sheet1) {Add-Member -InputObject $row -MemberType NoteProperty -Name "_Row"   -Value ($i ++) 
+                                                    Add-Member -InputObject $row -MemberType NoteProperty -Name "_Sheet" -Value  $worksheet1
+                                                    Add-Member -InputObject $row -MemberType NoteProperty -Name "_File"  -Value  $Referencefile} 
+    $i = $FirstDataRow ; foreach ($row in $Sheet2) {Add-Member -InputObject $row -MemberType NoteProperty -Name "_Row"   -Value ($i ++) 
+                                                    Add-Member -InputObject $row -MemberType NoteProperty -Name "_Sheet" -Value  $worksheet2
+                                                    Add-Member -InputObject $row -MemberType NoteProperty -Name "_File"  -Value  $Differencefile} 
+    
+    if ($ExcludeDifferent -and -not $IncludeEqual) {$IncludeEqual = $true} 
+    #Do the comparison and add file,sheet and row to the result - these are prefixed with "_" to show they are added the addition will fail if the sheet has these properties so split the operations 
+    [PSCustomObject[]]$diff = Compare-Object -ReferenceObject $Sheet1 -DifferenceObject $Sheet2 -Property $propList -PassThru -IncludeEqual:$IncludeEqual -ExcludeDifferent:$ExcludeDifferent  |
+                Sort-Object -Property "_Row","File"
+    
+    #if BackgroundColor was specified, set it on extra or extra or changed rows  
+    if      ($diff -and $BackgroundColor) {
+        #Differences may only exist in one file. So gather the changes for each file; open the file, update each impacted row in the shee, save the file  
+        $updates = $diff.where({$_.SideIndicator -ne "=="}) | Group-object -Property "_File"
+        foreach   ($file in $updates) {
+            try   {$xl  = Open-ExcelPackage -Path $file.name }
+            catch {Write-warning -Message "Can't open $($file.Name) for writing." ; return} 
+            if ($AllDataBackgroundColor) {
+                $file.Group._sheet | Sort-Object -Unique | ForEach-Object {
+                    $ws =  $xl.Workbook.Worksheets[$_] 
+                    if ($headerName) {$range = "A" +  $startrow      + ":" + $ws.dimension.end.address}
+                    else             {$range = "A" + ($startrow + 1) + ":" + $ws.dimension.end.address}
+                    Set-Format -WorkSheet $ws -BackgroundColor $AllDataBackgroundColor -Range $Range 
+                }
+            }
+            foreach ($row in $file.group)  {
+                $ws    = $xl.Workbook.Worksheets[$row._Sheet]
+                $range = $ws.Dimension -replace "\d+",$row._row
+                Set-Format -WorkSheet $ws -Range $range -BackgroundColor $BackgroundColor         
+            }
+            if ($TabColor) {
+                foreach ($tab in ($file.group._sheet | Select-Object -Unique)) {
+                    $xl.Workbook.Worksheets[$tab].TabColor = $TabColor
+                 }
+            }
+            $xl.save()  ; $xl.Stream.Close() ; $xl.Dispose()
+        }
+    }
+    #if font colour was specified, set it on changed properties where the same key appears in both sheets. 
+    if      ($diff -and $FontColor -and ($propList -contains $Key)  ) {
+        $updates = $diff.where({$_.SideIndicator -ne "=="})  | Group-object -Property $Key | Where-Object {$_.count -eq 2} 
+        if ($updates) {
+            $XL1 = Open-ExcelPackage -path $Referencefile
+            if ($oneFile ) {$xl2 = $xl1} 
+            else           {$xl2 = Open-ExcelPackage -path $Differencefile }
+            foreach ($u in $updates) {
+                 foreach ($p in $propList) {
+                    if ($u.group[0]._file -eq $Referencefile) {
+                        $ws1 =  $xl1.Workbook.Worksheets[$u.Group[0]._sheet]
+                        $ws2 =  $xl2.Workbook.Worksheets[$u.Group[1]._sheet]
+                    }
+                    else {
+                        $ws1 =  $xl2.Workbook.Worksheets[$u.Group[0]._sheet]
+                        $ws2 =  $xl1.Workbook.Worksheets[$u.Group[1]._sheet]
+                    }
+                    if($u.Group[0].$p -ne $u.Group[1].$p ) {
+                        Set-Format -WorkSheet $ws1 -Range ($Columns[$p] + $u.Group[0]._Row) -FontColor $FontColor
+                        Set-Format -WorkSheet $ws1 -Range ($Columns[$p] + $u.Group[1]._Row) -FontColor $FontColor
+                    } 
+                } 
+            }
+            $xl1.Save()                     ; $xl1.Stream.Close() ; $xl1.Dispose()
+            if (-not $oneFile) {$xl2.Save() ; $xl2.Stream.Close() ; $xl2.Dispose()}
+        }
+    }
+    elseif  ($diff -and $FontColor) {Write-Warning -Message "To match rows to set changed cells, you must specify -Key and it must match one of the included properties." }   
+
+    #if nothing was found write a message which wont be redirected
+    if (-not $diff) {Write-Host "Comparison of $Referencefile::$worksheet1 and $Differencefile::$WorkSheet2 returned no results."  }
+
+    if      ($show)               { 
+        Start-Process -FilePath $Referencefile 
+        if  (-not $oneFile)  { Start-Process -FilePath $Differencefile }
+        if  ($GridView)      { Write-Warning -Message "-GridView is ignored when -Show is specified" } 
+    }    
+    elseif  ($GridView -and $propList -contains $key) { 
+             
+             
+             if ($IncludeEqual -and -not $ExcludeDifferent) {
+                $GroupedRows = $diff | Group-Object -Property $key  
+             }
+             else { #to get the right now numbers on the grid we need to have all the rows. 
+                $GroupedRows = Compare-Object -ReferenceObject $Sheet1 -DifferenceObject $Sheet2 -Property $propList -PassThru -IncludeEqual  | 
+                                        Group-Object -Property $key                       
+             }
+             #Additions, deletions and unchanged rows will give a group of 1; changes will give a group of 2 .
+
+             #If one sheet has extra rows we can get a single "==" result from compare, but with the row from the reference sheet 
+             #but the row in the other sheet might so we will look up the row number from the key field build a hash table for that  
+             $Sheet2 | ForEach-Object -Begin {$Rowhash = @{} } -Process {$Rowhash[$_.$key] = $_._row } 
+
+             $ExpandedDiff = ForEach ($g in $GroupedRows)  {
+                #we're going to create a custom object from a hash table. We want the fields to be ordered
+                $hash = [ordered]@{}  
+                foreach ($result IN $g.Group) {
+                    # if result indicates equal or "in Reference" set the reference side row. If we did that on a previous result keep it. Otherwise set to "blank"
+                    if     ($result.sideindicator -ne "=>")      {$hash["<Row"] = $result._Row  } 
+                    elseif (-not $hash["<Row"])                  {$hash["<Row"] = "" }
+                    #if we have already set the side, this is the second record, so set side to indicate "changed"     
+                    if     ($hash.Side) {$hash.side = "<>"} else {$hash["Side"] = $result.sideindicator}
+                    #if result is "in reference" and we don't have a matching "in difference" (meaning a change) the lookup will be blank. Which we want.   
+                    $hash[">Row"] = $Rowhash[$g.Name] 
+                    #position the key as the next field (only appears once) 
+                    $Hash[$key]    = $g.Name  
+                    #For all the other fields we care about create <=FieldName and/or =>FieldName 
+                    foreach ($p in $propList.Where({$_ -ne $key})) {
+                        if  ($result.SideIndicator -eq "==")  {$hash[("=>$P")] = $hash[("<=$P")] =$result.$P}
+                        else                                  {$hash[($result.SideIndicator+$P)] =$result.$P}
+                    }
+                } 
+                [Pscustomobject]$hash
+             }
+
+             #Sort by reference row number, and fill in any blanks in the difference-row column
+             $ExpandedDiff = $ExpandedDiff | Sort-Object -Property "<row"  
+             for ($i = 1; $i -lt $ExpandedDiff.Count; $i++) {if (-not $ExpandedDiff[$i].">row") {$ExpandedDiff[$i].">row" = $ExpandedDiff[$i-1].">row" } }   
+             #Sort by difference row number, and fill in any blanks in the reference-row column
+             $ExpandedDiff = $ExpandedDiff | Sort-Object -Property ">row"  
+             for ($i = 1; $i -lt $ExpandedDiff.Count; $i++) {if (-not $ExpandedDiff[$i]."<row") {$ExpandedDiff[$i]."<row" = $ExpandedDiff[$i-1]."<row" } }  
+             
+             #if we had to put the equal rows back, take them out; sort, make sure all the columns are present in row 1 so the grid puts them in, and output              
+             if ( $ExcludeDifferent) {$ExpandedDiff = $ExpandedDiff.where({$_.side -eq "=="}) | Sort-Object -Property "<row" ,">row"  } 
+             elseif ( $IncludeEqual) {$ExpandedDiff = $ExpandedDiff                           | Sort-Object -Property "<row" ,">row"  }
+             else                    {$ExpandedDiff = $ExpandedDiff.where({$_.side -ne "=="}) | Sort-Object -Property "<row" ,">row"  } 
+             $ExpandedDiff | Update-FirstObjectProperties | Out-GridView -Title "Comparing $Referencefile::$worksheet1 (<=) with $Differencefile::$WorkSheet2 (=>)"   
+    }
+    elseif  ($GridView     )  {Write-Warning -Message "To use -GridView you must specify -Key and it must match one of the included properties."  }   
+    elseif  (-not $PassThru)  {return ($diff | Select-Object -Property (@(@{n="_Side";e={$_.SideIndicator}},"_File" ,"_Sheet","_Row") + $propList))}
+    if      (     $PassThru)  {return  $diff }
+}
+
+>>>>>>> 9f7884f991c80448091ef56853027f64d98b6cc7