How about this...
A1=2/13/2009 9:00
A2=2/15/2009 18:00
A3=(DAY(A2-A1)*24+HOUR(A2-A1)) // Number of hours between dates = 57
A4=QUOTIENT(A3,8) // Number of 8 hour days =
7
A5=MOD(A3,8) // Number of
remaining hours = 1
Then you can combine A4 and A5 as you like to use in later calcuations?
The approach for not counting weekends is a bit more complicated...
A1=2/13/2009 23:58
A2=2/16/2009 00:04
A3=((NETWORKDAYS(A1,A2)-2)*24)+((24-HOUR(A1))-(MINUTE(A1))/60)+((HOUR(A2))+MINUTE(A2)/60)
Will result in A3 containing 0.10, which represents 0.10 of an hour, or 6
mins. I'll leave it for you to experiment with what results this gives you
for other times and how you can then use a similar approach to that above to
split it out into days, hours, mins depending on how you want to use the
values later.
Cheers,
Scott