I have a Monte Carlo analysis that runs on my Excel 97 and as desired
will run for as many hours as I allow it. It's a bunch of spreadsheet
code that's tied together by a fairly simple VBA macro to plug
semi-random numbers into the spreadsheet and monitor the results.

If Excel is the only program active, then all is well and it will run to
conclusion in 10 hours or so. However when something else is running
such as a browser, e-mail, screen saver, etc., it will regularly lock up
Excel and XP reports it as "program not responding". Closing Excel is
the only answer.

My question is whether I've overlooked something in VBA that one needs
to do to periodically relinquish control of the system or something? I
wouldn't think such a thing would be necessary, but I can't imagine what
else is going on.

Thanks...

Bill