I thought I had answered this somewhere but I can't find it!
Use Scheduled Tasks (see windows help) in control panel
(win2kpro),when it asks for the programme to run, choose the xls file
instead, by browsing to it.

Now make sure a
Private Sub Workbook_Open()
procedure in the ThisWorkbook code of that xls file has the necessary
code, or calls to the code that you want executing, and that
ultimately somewhere, if you want, the code to close and/or save the
workbook.