Date/Time Calculation - cannot use networkday - I have a working formula except holidays

I am using this formula to get the answer I need when subtracting one date/time column from another except I have a range of holidays that I need to subtract from these columns as well. My answer is in hours. Everything works unless there is a holiday.

=24*((INT(AC2)-WEEKDAY(INT(AC2),2)+WEEKDAY(INT(AA2),2)-INT(AA2))/7*5-MIN(5,WEEKDAY(INT(AA2),2))+MIN(5,WEEKDAY(INT(AC2),2))+IF(WEEKDAY(AA2,2)<6,1-MOD(AA2,1),0)+IF(WEEKDAY(AC2,2)<6,MOD(AC2,1)-1,0))

I have a list of holidays in these cells $AO$2:$AO$21

yes I could not get the first formula to work. Kept getting reference error. This is a 24 hour cycle so Networkdays really messes me up (at least with my limited bit of working with formulas and functions). daddylonglegs I will try this. The start and end times can be anytime but there is a service level that we provide and we don't count weekends and holiday time against the service level. thanks!

Thanks Daddylonglegs! I have spent hours trying to make something work! Your formula worked perfectly.