Why does this work when used in PowerPoint 2003

Public Function FindWorksheet(myXLBook As Excel.Workbook, _
myWSCodename As String) As Excel.Worksheet

Set FindWorksheet = Nothing

On Error Resume Next
Set FindWorksheet =
myXLBook.Worksheets(CStr(myXLBook.VBProject.VBComp onents(myWSCodename).Properties("Name")))
On Error GoTo 0

End Function

And it doesn't work in PowerPoint 2007. I have confirmed that there is a
worksheet in myXLBook that matches myWSCode name.

Thanks!

Barb Reinhardt