Sounds like a situation where a multi-core system would be ideal: Excel
versions prior to Excel2007 do single-threaded calculation so you would only
be using 1 cpu leaving the other free.
(In Excel 2007 you can control how many calculation threads to use).


BTW if you are using range.calculate in your montecarlo simulation it runs a
lot faster in excel versions 97 and 2000 than 2002 /2003.

regards
Charles
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"Bill Martin" wrote in message
...
I'm not sure if this is a VBA question, an Excel question, or an XP
question, but is there a way to limit how much CPU Excel burns?

I've written a macro that will endlessly run a Monte Carlo solution.
Normally I run it overnight and all is well. Sometimes however I run it
during the day, particularly if I'm tinkering with the code and want to
run it in the background to watch how it performs. When I do this it pegs
CPU usage at 100% and makes everything else on the machine painfully
sluggish.

Is there some way to cut back on how much CPU Excel consumes? Ideally I'd
like my VBA routine to periodically sample CPU usage and adjust what Excel
consumes. Alternatively, is there someway I can manually adjust it?

Thanks.

Bill