Function Add-ConditionalFormatting {
    <#
      .Synopsis
        Adds conditional formatting to all or part of a worksheet.
      .Description
        Conditional formatting allows Excel to:
        * Mark cells with icons depending on their value
        * Show a databar whose length indicates the value or a two or three color scale where the color indicates the relative value
        * Change the color, font, or number format of cells which meet given criteria
        Add-ConditionalFormatting allows these parameters to be set; for fine tuning of
        the rules, the -PassThru switch will return the rule so that you can modify
        things which are specific to that type of rule, example, the values which
        correspond to each icon in an Icon-Set.
      .Example
        >
        $excel = $avdata | Export-Excel -Path (Join-path $FilePath "\Machines.XLSX" ) -WorksheetName "Server Anti-Virus" -AutoSize -FreezeTopRow -AutoFilter -PassThru
        Add-ConditionalFormatting -WorkSheet $excel.Workbook.Worksheets[1] -Address "b2:b1048576" -ForeGroundColor "RED"     -RuleType ContainsText -ConditionValue "2003"
        Add-ConditionalFormatting -WorkSheet $excel.Workbook.Worksheets[1] -Address "i2:i1048576" -ForeGroundColor "RED"     -RuleType ContainsText -ConditionValue "Disabled"
        $excel.Workbook.Worksheets[1].Cells["D1:G1048576"].Style.Numberformat.Format = [cultureinfo]::CurrentCulture.DateTimeFormat.ShortDatePattern
        $excel.Workbook.Worksheets[1].Row(1).style.font.bold = $true
        $excel.Save() ; $excel.Dispose()

        Here Export-Excel is called with the -PassThru parameter so the ExcelPackage object
        representing Machines.XLSX is stored in $Excel.The desired worksheet is selected
        and then columns" B" and "I" are conditionally formatted (excluding the top row)
        to show red text if they contain "2003" or "Disabled" respectively.
        A fixed date format is then applied to columns D to G, and the top row is formatted.
        Finally the workbook is saved and the Excel package object is closed.
      .Example
        >
        $r = Add-ConditionalFormatting -WorkSheet $excel.Workbook.Worksheets[1] -Range "B1:B100" -ThreeIconsSet Flags -Passthru
        $r.Reverse = $true ;   $r.Icon1.Type = "Num"; $r.Icon2.Type = "Num" ; $r.Icon2.value = 100 ; $r.Icon3.type = "Num" ;$r.Icon3.value = 1000

        Again Export-Excel has been called with -PassThru leaving a package object
        in $Excel. This time B1:B100 has been conditionally formatted with 3 icons,
        using the "Flags" Icon-Set. Add-ConditionalFormatting does not provide access
        to every option in the formatting rule, so -PassThru has been used and the
        rule is modified to apply the flags in reverse order, and transitions
        between flags are set to 100 and 1000.
      .Example
        Add-ConditionalFormatting -WorkSheet $sheet -Range "D2:D1048576" -DataBarColor Red

        This time $sheet holds an ExcelWorkshseet object and databars are added to
        column D, excluding the top row.
      .Example
        Add-ConditionalFormatting -Address $worksheet.cells["FinishPosition"] -RuleType Equal -ConditionValue 1 -ForeGroundColor Purple -Bold -Priority 1 -StopIfTrue

        In this example a named range is used to select the cells where the condition
        should apply, and instead of specifying a sheet and range within the sheet as
        separate parameters, the cells where the format should apply are specified
        directly. If a cell in the "FinishPosition" range is 1, then the text is
        turned to Bold & Purple. This rule is moved to first in the priority list,
        and where cells have a value of 1, no other rules will be processed.
      .Example
        >
        $excel = Get-ChildItem | Select-Object -Property Name,Length,LastWriteTime,CreationTime | Export-Excel "$env:temp\test43.xlsx" -PassThru -AutoSize
        $ws = $excel.Workbook.Worksheets["Sheet1"]
        $ws.Cells["E1"].Value = "SavedAt"
        $ws.Cells["F1"].Value = [datetime]::Now
        $ws.Cells["F1"].Style.Numberformat.Format = (Expand-NumberFormat -NumberFormat 'Date-Time')
        $lastRow = $ws.Dimension.End.Row

        Add-ConditionalFormatting -WorkSheet $ws -address "A2:A$Lastrow" -RuleType LessThan    -ConditionValue "A"  -ForeGroundColor Gray
        Add-ConditionalFormatting -WorkSheet $ws -address "B2:B$Lastrow" -RuleType GreaterThan -ConditionValue  1000000         -NumberFormat '#,###,,.00"M"'
        Add-ConditionalFormatting -WorkSheet $ws -address "C2:C$Lastrow" -RuleType GreaterThan -ConditionValue "=INT($F$1-7)"  -ForeGroundColor Green  -StopIfTrue
        Add-ConditionalFormatting -WorkSheet $ws -address "D2:D$Lastrow" -RuleType Equal       -ConditionValue "=C2"           -ForeGroundColor Blue   -StopIfTrue

        Close-ExcelPackage -Show $excel

        The first few lines of code export a list of file and directory names, sizes
        and dates to a spreadsheet. It puts the date of the export in cell F1.
        The first Conditional format changes the color of files and folders that begin
        with a ".", "_" or anything else which sorts before "A".
        The second Conditional format changes the Number format of numbers bigger than
        1 million, for example 1,234,567,890 will dispay as "1,234.57M"
        The third highlights datestamps of files less than a week old when the export
        was run; the = is necessary in the condition value otherwise the rule will
        look for the the text INT($F$1-7), and the cell address for the date is fixed
        using the standard Excel $ notation.
        The final Conditional format looks for files which have not changed since they
        were created. Here the condition value is "=C2". The = sign means C2 is treated
        as a formula, not literal text. Unlike the file age, we want the cell used to
        change for each cell where the conditional format applies. The first cell in
        the conditional format range is D2, which is compared against C2, then D3 is
        compared against C3 and so on. A common mistake is to include the title row in
        the range and accidentally apply conditional formatting to it, or to begin the
        range at row 2 but use row 1 as the starting point for comparisons.
      .Example
        Add-ConditionalFormatting  $ws.Cells["B:B"] GreaterThan 10000000 -Fore  Red -Stop -Pri 1

        This version shows the shortest syntax - the Address, Ruletype, and
        Conditionvalue can be identified from their position, and ForegroundColor,
        StopIfTrue and Priority can all be shortend.

    #>
    Param (
        #A block of cells to format - you can use a named range with -Address $ws.names[1] or  $ws.cells["RangeName"]
        [Parameter(Mandatory = $true, Position = 0)]
        [Alias("Range")]
        $Address ,
        #The worksheet where the format is to be applied
        [OfficeOpenXml.ExcelWorksheet]$WorkSheet ,
        #A standard named-rule - Top / Bottom / Less than / Greater than / Contains etc.
        [Parameter(Mandatory = $true, ParameterSetName = "NamedRule", Position = 1)]
        [OfficeOpenXml.ConditionalFormatting.eExcelConditionalFormattingRuleType]$RuleType ,
        #Text color for matching objects
        [Parameter(ParameterSetName = "NamedRule")]
        [Alias("ForegroundColour")]
        $ForegroundColor,
        #Color for databar type charts
        [Parameter(Mandatory = $true, ParameterSetName = "DataBar")]
        [Alias("DataBarColour")]
        $DataBarColor,
        #One of the three-icon set types (e.g. Traffic Lights)
        [Parameter(Mandatory = $true, ParameterSetName = "ThreeIconSet")]
        [OfficeOpenXml.ConditionalFormatting.eExcelconditionalFormatting3IconsSetType]$ThreeIconsSet,
        #A four-icon set name
        [Parameter(Mandatory = $true, ParameterSetName = "FourIconSet")]
        [OfficeOpenXml.ConditionalFormatting.eExcelconditionalFormatting4IconsSetType]$FourIconsSet,
        #A five-icon set name
        [Parameter(Mandatory = $true, ParameterSetName = "FiveIconSet")]
        [OfficeOpenXml.ConditionalFormatting.eExcelconditionalFormatting5IconsSetType]$FiveIconsSet,
        #Use the Icon-Set in reverse order, or reverse the orders of Two- & Three-Color Scales
        [Parameter(ParameterSetName = "NamedRule")]
        [Parameter(ParameterSetName = "ThreeIconSet")]
        [Parameter(ParameterSetName = "FourIconSet")]
        [Parameter(ParameterSetName = "FiveIconSet")]
        [switch]$Reverse,
        #A value for the condition (for example 2000 if the test is 'lessthan 2000'; Formulas should begin with "=" )
        [Parameter(ParameterSetName = "NamedRule",Position = 2)]
        $ConditionValue,
        #A second value for the conditions like "Between X and Y"
        [Parameter(ParameterSetName = "NamedRule",Position = 3)]
        $ConditionValue2,
        #Background color for matching items
        [Parameter(ParameterSetName = "NamedRule")]
        $BackgroundColor,
        #Background pattern for matching items
        [Parameter(ParameterSetName = "NamedRule")]
        [OfficeOpenXml.Style.ExcelFillStyle]$BackgroundPattern = [OfficeOpenXml.Style.ExcelFillStyle]::None ,
        #Secondary color when a background pattern requires it
        [Parameter(ParameterSetName = "NamedRule")]
        $PatternColor,
        #Sets the numeric format for matching items
        [Parameter(ParameterSetName = "NamedRule")]
        $NumberFormat,
        #Put matching items in bold face
        [Parameter(ParameterSetName = "NamedRule")]
        [switch]$Bold,
        #Put matching items in italic
        [Parameter(ParameterSetName = "NamedRule")]
        [switch]$Italic,
        #Underline matching items
        [Parameter(ParameterSetName = "NamedRule")]
        [switch]$Underline,
        #Strikethrough text of matching items
        [Parameter(ParameterSetName = "NamedRule")]
        [switch]$StrikeThru,
        #Prevent the processing of subsequent rules
        [Parameter(ParameterSetName = "NamedRule")]
        [switch]$StopIfTrue,
        #Set the sequence for rule processing
        [int]$Priority,
        #If specified pass the rule back to the caller to allow additional customization.
        [switch]$PassThru
    )

    #Allow conditional formatting to work like Set-ExcelRange (with single ADDRESS parameter), split it to get worksheet and range of cells.
    If ($Address -is [OfficeOpenXml.Table.ExcelTable]) {
            $WorkSheet = $Address.Address.Worksheet
            $Address   = $Address.Address.Address
    }
    elseif  ($Address.Address -and $Address.Worksheet -and -not $WorkSheet) { #Address is a rangebase or similar
        $WorkSheet = $Address.Worksheet[0]
        $Address   = $Address.Address
    }
    elseif ($Address -is [String] -and $WorkSheet -and $WorkSheet.Names[$Address] ) { #Address is the name of a named range.
        $Address = $WorkSheet.Names[$Address].Address
    }
    if (($Address -is [OfficeOpenXml.ExcelRow]    -and -not $WorkSheet) -or
        ($Address -is [OfficeOpenXml.ExcelColumn] -and -not $WorkSheet) ){  #EPPLUs Can't get the worksheet object from a row or column object, so bail if that was tried
        Write-Warning -Message "Add-ConditionalFormatting does not support Row or Column objects as an address; use a worksheet and/or specify 'R:R' or 'C:C' instead. "; return
    }
    elseif ($Address -is [OfficeOpenXml.ExcelRow]) {  #But if we have a column or row object and a worksheet (I don't know *why*) turn them into a string for the range
            $Address = "$($Address.Row):$($Address.Row)"
    }
    elseif ($Address -is [OfficeOpenXml.ExcelColumn]) {
        $Address = [OfficeOpenXml.ExcelAddress]::new(1,$address.ColumnMin,1,$address.ColumnMax).Address -replace '1',''
        if ($Address -notmatch ':') {$Address = "$Address`:$Address"}
    }
    if ( $Address -is [string] -and $Address -match "!") {$Address = $Address -replace '^.*!',''}
    #By this point we should have a worksheet object whose ConditionalFormatting collection we will add to. If not, bail.
    if (-not $worksheet -or $WorkSheet -isnot [OfficeOpenXml.ExcelWorksheet]) {write-warning "You need to provide a worksheet object." ; return}
    #region create a rule of the right type
    if     ($RuleType -match 'IconSet$') {Write-warning -Message "You cannot configure a Icon-Set rule in this way; please use -$RuleType <SetName>." ; return}
    if ($PSBoundParameters.ContainsKey("DataBarColor"  )      ) {if ($DataBarColor -is [string]) {$DataBarColor = [System.Drawing.Color]::$DataBarColor }
                                                                     $rule =  $WorkSheet.ConditionalFormatting.AddDatabar(     $Address , $DataBarColor )
    }
    elseif ($PSBoundParameters.ContainsKey("ThreeIconsSet" )      ) {$rule =  $WorkSheet.ConditionalFormatting.AddThreeIconSet($Address , $ThreeIconsSet)}
    elseif ($PSBoundParameters.ContainsKey("FourIconsSet"  )      ) {$rule =  $WorkSheet.ConditionalFormatting.AddFourIconSet( $Address , $FourIconsSet )}
    elseif ($PSBoundParameters.ContainsKey("FiveIconsSet"  )      ) {$rule =  $WorkSheet.ConditionalFormatting.AddFiveIconSet( $Address , $FiveIconsSet )}
    else                                                            {$rule = ($WorkSheet.ConditionalFormatting)."Add$RuleType"($Address )                }
    if     ($Reverse)  {
            if     ($rule.type -match 'IconSet$'   )                {$rule.reverse = $true}
            elseif ($rule.type -match 'ColorScale$')                {$temp =$rule.LowValue.Color ; $rule.LowValue.Color = $rule.HighValue.Color; $rule.HighValue.Color = $temp}
            else   {Write-Warning -Message "-Reverse was ignored because $ruletype does not support it."}
    }
    #endregion
    #region set the rule conditions
    #for lessThan/GreaterThan/Equal/Between conditions make sure that strings are wrapped in quotes. Formulas should be passed with = which will be stripped.
    if     ($RuleType -match "Than|Equal|Between" ) {
        if  ($PSBoundParameters.ContainsKey("ConditionValue" )) {
                $number = $Null
                #if the condition type is not a value type, but parses as a number, make it the number
                if ($ConditionValue -isnot [System.ValueType] -and [Double]::TryParse($ConditionValue, [System.Globalization.NumberStyles]::Any, [System.Globalization.NumberFormatInfo]::CurrentInfo, [Ref]$number) ) {
                         $ConditionValue  = $number
                } #else if it is not a value type, or a formula, or wrapped in quotes, wrap it in quotes.
                elseif (($ConditionValue -isnot [System.ValueType])-and ($ConditionValue  -notmatch '^=') -and ($ConditionValue  -notmatch '^".*"$') ) {
                         $ConditionValue  = '"' + $ConditionValue +'"'
                }
        }
        if  ($PSBoundParameters.ContainsKey("ConditionValue2")) {
                $number = $Null
                if ($ConditionValue -isnot [System.ValueType] -and [Double]::TryParse($ConditionValue2, [System.Globalization.NumberStyles]::Any, [System.Globalization.NumberFormatInfo]::CurrentInfo, [Ref]$number) ) {
                         $ConditionValue2 = $number
                }
                elseif (($ConditionValue -isnot [System.ValueType]) -and ($ConditionValue2 -notmatch '^=') -and ($ConditionValue2 -notmatch '^".*"$') ) {
                         $ConditionValue2  = '"' + $ConditionValue2 + '"'
                }
        }
    }
    #But we don't usually want quotes round containstext | beginswith type rules. Can't be Certain they need to be removed, so warn the user their condition might be wrong
    if     ($RuleType -match "Text|With" -and $ConditionValue -match '^".*"$'  ) {
            Write-Warning -Message "The condition will look for the quotes at the start and end."
    }
    if     ($PSBoundParameters.ContainsKey("ConditionValue" ) -and
            $RuleType -match "Top|Botom"                          ) {$rule.Rank      = $ConditionValue }
    if     ($PSBoundParameters.ContainsKey("ConditionValue" ) -and
            $RuleType -match "StdDev"                             ) {$rule.StdDev    = $ConditionValue }
    if     ($PSBoundParameters.ContainsKey("ConditionValue" ) -and
            $RuleType -match "Than|Equal|Expression"              ) {$rule.Formula   = ($ConditionValue  -replace '^=','') }
    if     ($PSBoundParameters.ContainsKey("ConditionValue" ) -and
            $RuleType -match "Text|With"                          ) {$rule.Text      = ($ConditionValue  -replace '^=','') }
    if     ($PSBoundParameters.ContainsKey("ConditionValue" ) -and
            $PSBoundParameters.ContainsKey("ConditionValue2") -and
            $RuleType -match "Between"                            ) {
                                                                     $rule.Formula   = ($ConditionValue  -replace '^=','');
                                                                     $rule.Formula2  = ($ConditionValue2 -replace '^=','')
    }
    if     ($PSBoundParameters.ContainsKey("StopIfTrue")          ) {$rule.StopIfTrue = $StopIfTrue }
    if     ($PSBoundParameters.ContainsKey("Priority")            ) {$rule.Priority   = $Priority }
    #endregion
    #region set the rule format
    if     ($PSBoundParameters.ContainsKey("NumberFormat"     )   ) {$rule.Style.NumberFormat.Format        = (Expand-NumberFormat  $NumberFormat)             }
    if     ($Underline                                            ) {$rule.Style.Font.Underline             = [OfficeOpenXml.Style.ExcelUnderLineType]::Single }
    elseif ($PSBoundParameters.ContainsKey("Underline"        )   ) {$rule.Style.Font.Underline             = [OfficeOpenXml.Style.ExcelUnderLineType]::None   }
    if     ($PSBoundParameters.ContainsKey("Bold"             )   ) {$rule.Style.Font.Bold                  = [boolean]$Bold       }
    if     ($PSBoundParameters.ContainsKey("Italic"           )   ) {$rule.Style.Font.Italic                = [boolean]$Italic     }
    if     ($PSBoundParameters.ContainsKey("StrikeThru"       )   ) {$rule.Style.Font.Strike                = [boolean]$StrikeThru }
    if     ($PSBoundParameters.ContainsKey("ForeGroundColor"  )   ) {if ($ForeGroundColor -is [string])      {$ForeGroundColor = [System.Drawing.Color]::$ForeGroundColor }
                                                                     $rule.Style.Font.Color.color           = $ForeGroundColor     }
    if     ($PSBoundParameters.ContainsKey("BackgroundColor"  )   ) {if ($BackgroundColor -is [string])      {$BackgroundColor = [System.Drawing.Color]::$BackgroundColor }
                                                                     $rule.Style.Fill.BackgroundColor.color = $BackgroundColor     }
    if     ($PSBoundParameters.ContainsKey("BackgroundPattern")   ) {$rule.Style.Fill.PatternType           = $BackgroundPattern   }
    if     ($PSBoundParameters.ContainsKey("PatternColor"     )   ) {if ($PatternColor -is [string])         {$PatternColor = [System.Drawing.Color]::$PatternColor }
                                                                     $rule.Style.Fill.PatternColor.color    = $PatternColor        }
    #endregion
    #Allow further tweaking by returning the rule, if passthru specified
    if     ($Passthru)  {$rule}
}