This article may get you going on the right track.

http://support.microsoft.com/kb/2140...22120121120120

"Charlie Zinck" wrote:

I'm trying to calculate the difference between start and finish times of
projects, and it needs to be in 1/100 time. for example 1:30 - 3:00 would
1:50. I haven't been able to figure out a formula for excel 2000.

Any help would be greatly appreciated.