Calculate Duration of Time for an Employee

[SarjuP]

I want to do the calculation on ‘xyz’ memory table in Clarion:
I have fields loaded in Memory table from reading a .Dat file as:
Emp No. Shift PunchType LastName FirstName Date PunchTime
111111111 1 1 John Doe 04/24/2011 7:30 AM
111111111 1 2 John Doe 04/24/2011 4:00 PM

Things I want ToDo:
1)I want to calculate the Duration(in time hours) of a particular employee depending upon his Shift
For eg. Shift 1 will have a lunch break and will deduct 30 mins from the total duration time.
2)Shift 2 will not have a lunch break and should give me total duration of time.
3)Shift 3 will be little bit different to calculate, though there will be no lunch.
For example : If PunchTime(In) on date 04/24/2011 will be 11:00pm and PunchTime(out) on 04/25/2011 will be at 4:30am.

Thanks,
Sarju.