calculating time in 24hr clock with added conditions

I think Zbor's suggestion should be like this

=IF(J7="","",IF(OR(G7="P1",G7="PIC"),MOD(K7-J7,1),""))

That assumes you have times in J7 and K7. If you want to type in just 2350 and 0700 without the colons then format as you suggested and use this version

=IF(J7="","",IF(OR(G7="P1",G7="PIC"),MOD(TEXT(K7,"00\:00")-TEXT(J7,"00\:00"),1),""))

to input the times you can omit leading zeroes so for 07:00 AM you can just input 700

Daddylonglegs - Thank you very much. It all works, I'm goig to use the the 24 hour clock without the colons as it seems to perform perfectly. I really appreciate your help. Can you foresee any problems using the the 24 hour clock this way, all I ever want it to do is just add to up, it isn't restricted to a certain number is it? as it might eventually have to count over a 1000 hours or more. I have checked your formula against ZBOR and the only difference that I could see was a space between the comma and the word MOD

What will be over 1000 hours? If you are summing columns L or M to get those sums then that won't be a problem - those result columns will still be in "real time" format.