Excel 2007 : Autofilter Colour Heading Cell with filter

I have code taken from another source (not sure if Im allowed to say what website I got it from - but incase not - I'd like to thank the author)

Basically it highlights the top cell in a filtered range, if there is a filter in place on that column. So far so good. The problem I have is that If I then open another workbook, its applying the same rule. I want the code only to apply to the original workbook. I believe the problem is that the code references activesheet and therefore is triggered by any other open workbook. How can I change the code so that it only runs on the workbook for which it was intended. The code is as follows:

In Thisworkbook

Private Sub Workbook_SheetCalculate(ByVal Sh As Object)
Application.Windows("Error Logs.xlsm").Activate
If Sh.AutoFilterMode Then ColorDisplayFilter
End Sub

and then in a separate module

Sub ColorDisplayFilter()
Application.Windows("Error Logs.xlsm").Activate
    Dim flt As Filter
    Dim iCol As Integer
    Dim lRow As Long

    iCol = 0
    lRow = ActiveSheet.AutoFilter.Range.Row
    Application.EnableEvents = False
    For Each flt In ActiveSheet.AutoFilter.Filters
        iCol = iCol + 1
        If flt.On Then
            Cells(lRow, iCol).Interior.ColorIndex = 26
        Else
            Cells(lRow, iCol).Interior.ColorIndex = 3
        End If
    Next flt
    Application.EnableEvents = True
End Sub

I've tried changing activesheet to thisworkbook but that returns an error?

Any help would be greatly appreciated.

Thank you in advance.