First, you'd have to have some way of starting the workbook that contained the
ontime macro. Maybe manual or some sort of windows scheduling program?????
Then you'd have to make sure that macros are allowed to run (if you're not there
to click any buttons).
And then the .ontime macro would run when specified.
Be aware that if you close that workbook that is going to have that macro run
via ontime (but keep excel open), excel will open that workbook to get to that
ontime macro.
If you close excel, then the ontime macro won't run.
If you want to close that "master" workbook and kill the ontime procedure, you
can do that, too.
In fact, I'd start here (Chip Pearson's site) to learn more about .ontime:
http://www.cpearson.com/excel/OnTime.aspx