problem auto_open procedure

I've this kind of problem.

I've written a routine (in Excel 97) that open another workbook (i.e. pippo.xls). In this workbook (pippo.xls) there is an event procedure (Workbook_Open()) in the Thisworkbook object.
With this event procedure I would to open new text file or copy/add some worksheets in other location but the procedure doesn't work.
Why?
Note: if I launch the event procedure from pippo.xls the routine works good.
The there is problem, when I open pippo.xls from another workbook.

example
Private Sub Workbook_Open()
Dim today As Stringtoday = Format(Now(), "dd-mm")
If Worksheets(1).Name = today
Then Exit Sub
Else
Worksheets(1).Copy before:=Worksheets(1)Worksheets(1).Name = today
ActiveSheet.Shapes.Range(Array("Button4")).Delete

''''' at this point the procedure doesn't work because the new worksheet hasn't been added, and shapes are not ''''' selected

End If
End Sub

Many Thanks for your help.