Caculating the Time difference from Start & end date/time excludin weekends & non ofce hrs

Im using an Excel 2003 & i need to calculate the net process or respond time excluding
1. weekends &
2. non working hours

My excel sheets contains:-
A2:- Start date
B2:- Start time
C2:- Stop date
D2:- Stop time
E2:- needs to show the difference of the time in minutes
(If required, the start date & time can be combined to one cell)

Working hours will be:-
Monday to Friday:- 06:30 to 22:00 hrs (IST)
Saturday 09:30 to 13:00 hrs (IST)

Weekends with be:-
Saturdays (After 13:00 hrs) + Sundays (Whole day) + Monday 06:30 hrs

Plse help me out whether there is any possibilities to set up such formula in excel 2003.
This will reduce lots of work from my end

Dear Legs,

The below formula works. However, just wanna inform you that my start date & time cannot be only in working days & hours. It will be outside the working hours or even in weekend.

So, can you plse advise the formula for the same too.

Can anybody assist on this formula

The above formula works. However, there are still some condition wherein the time still shows incorrect format.

Start date Start time Stop date Stop time Difference Comments
05-07-2012 15:46 06-07-2012 10:46 10:30 Working fine
06-07-2012 23:00 07-07-2012 10:30 1:00 Working fine
07-07-2012 14:00 09-07-2012 07:30 1:00 Weekends timing works fine
04-07-2012 18:00 06-07-2012 10:00 23:00 Two difference time calculation working fine.
04-07-2012 18:00 06-07-2012 16:00 5:00 Not showing the calculation properly
time calculation should be 4hrs(04-07-2012)+15:30 hrs(05-07-2012)+9:30 hrs(06-07-2012)= 29 hrs
However, it only shows 5 hrs, excluding the 24 hrs (which is one day)

I tried to format the cell using [h] to show it in hours, but still the result remains the same.
But when i tried to convert it in the minutes, (E2*1440), the output is perfect

Can you plse let me know how can i format the cell in the Difference (e2) to show the time as 29 hrs i/o 5 hrs for the 5th set-up highlighted in Blue