Yes, but the catch is you need an instance of Excel which contains the
Ontime code running in the background for this to happen. At the
appointed hour, this can then open a workbook and do stuff.

Although I haven't tried this, could you use the windows Task Scheduler
instead? Just thinking aloud, if you used this to open Excel at - say -
7.25, then set up an Excel add-in or personal macro workbook with
Auto_Open code for your Ontime, then you might be able to do away with
Excel running in the background. You could also give your code the
weekend off if you went this way.

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.