Macro runs fine, but hangs if I try to work on another window

[Rruffpaw]

I have a very large Excel spreadsheet (13 MB) with several macros. One
of them runs a loop with multiple commands.

The macro runs fine, as long as I sit back and just watch it run. If I
click on another window however, it invariably freezes and I have to
terminate Excel.

Any ideas on how I can remedy this?

I'm running Excel 2003 on Windows XP, but have noticed the same
problem with the same spreadsheet on a machine running Excel 2007,
also on Windows XP.

Thanks

-Sharat