I'm trying to work out the working hours between two specific dates,
but cannot get my head around it.

In cell K2 is actual_start, which is formatted to show me 30-06-2009
15:00, and L2 is actual_end, formatted the same way, say 04-10-2009
8:15.

I need to know the working hours between the two dates, based on a
standard business working day of 8:30am to 5:00pm.

I can work out in my head that it's 27 working days, but actual_start
day is only 2 hours of the working day, then 25 days of 8.5 hours, and
last day nothing! Trouble is, I have to do this for approximately
5,000 rows each month. Can anyone please help with a formula or
advice?

Thanks in anticipation

Pete