I need to find the time spent on a call ticket from:

7/07/06 3:30 p.m to 7/09/06 1:30 p.m.

Now, the problem is that I don't want the total days and hours. I need to
know how much time was spent on this call ticket that was opened on 7/07 at
3:30 p.m. and it was closed on 7/09 at 1:30 p.m. I can calculate it
manually.... 1 hour on 7/07 and 6.5 hours on 7/09, then it was closed... so
the total time spent on the call ticket being open is 7.5 hours

The glitch is that I only want it to calculate the time between our business
hours of 7:00 a.m. thru 4:30 p.m., not a 24 day.

Thanks, Lisa