Hi !! I have a table as below :

Date Time IN Date Time Out No. of hrs
01/09/2008 23:30 02/09/2008 1:30 2.00
02/09/2008 22:00 03/09/2008 2:30 4.30
03/09/2008 23:00 04/09/2008 0:30 1.30
04/09/2008 0:20 05/09/2008 0:50 0.30
05/09/2008 1:00 05/09/2008 2:00 1.00
06/09/2008 2:00 06/09/2008 3:00 1.00
07/09/2008 3:00 07/09/2008 4:00 1.00
08/09/2008 4:00 08/09/2008 5:00 1.00

Each day i record the vehicle in & out time at the warehouse.
1.) How can i automatically calculate the no of hrs the vehicle was at the wh.
2.) A also need the total no of hrs for a select period.
3.) How do i calculate the average time vehicle reaches the wh for a period.
4.) How do i calculate the average time vehicle leaves the wh for a period.
Simple average is not giving the correct result for IN-TIME & OUT-TIME ,
since in some case there is a change in the dates as well. Vehicle come in
the night but leaves post midnight when the date has also changed.
Pls. help me with this problem.
regards
Sansk_23