I use the following code to control program flow on startup. It works fine on
2 other PCs (and worked on my PC last week), but (now) I get "run-time error
'9': Subscript out of range" when it runs on my PC.

Any ideas what might be different between the two PCs that causes it to
bomb? I have tried rebooting and compared vba references between the two PCs
-can't see anything obvious. Would appreciate any suggestions.
*****

Sub Workbook_Open()
If WorkbookExists("UPE_Period.xls") Then
BuildALL
Else
Sheets("Reports").Select
End If
End Sub
******
Public Function WorkbookExists(WorkbookName As String) As Boolean
On Error Resume Next
If Application.Workbooks(WorkbookName) Is Nothing Then
WorkbookExists = False
Else
WorkbookExists = True
End If
End Function