subtraction formula

Hello

I want to build one formula depending upon the number or working hours.

In the sheet suppose i have following columns

e.g

Employee Name DateIn Timein DateOut Timeout Dept Shift Reg OT
John 1/2/03 11:00 1/2/03 7:00 HR First 8:00


So i want to write one formula in which if reg > 5 then automatically in Ot column it will subtract 8-5 and show OT as 3

So how i should write formula?

=IF(H7>$U$4,H7-$U$4,)

H7 is the value where Reg column shows values. So if i want to extract extra hours then i should write above formula to solve this problem


U4 is the total working hours