Excel 2002

I have 2 fields that are each formatted with date time. I am able to
subtract the most recent one from the older one to give me a difference in
hours:minutes.

Now the tricky part. I'm not sure if this is even possible in Excel, but our
company runs our business on an 8-5 M-F schedule. The difference in the
dates/time can be as long as a couple of weeks. I need to somehow do the
calculating while taking out any hours that do not fall within M-F 8-5.

Thanks

Gary