Need help on COMPLEX Time calculations

Title

Need help on COMPLEX Time calculations

Post

I have a situation where an employee shift starts at 11:00 PM on a Thursday for example. The employee shift ends at 7:30 am Friday (the next day).

Here is the calculation that I use to figure hours worked because of the shift starting on one day and ending on the following day:

Case ( Exclude Lunch = "YES" ;  Round ((( TimestampEnd - TimestampStart)  / 3600)-.5 ; 2 ); Exclude Lunch = "NO" ;  Round (( TimestampEnd - TimestampStart)  / 3600 ; 2 ))

Here is where I need to get more technical

The one hour before Thursday midnight is a different pay scale than the 7-1/2 hours on Friday morning midnight shift.

FIRST Calculation Result - I need to create a calculation that takes the timestamped one hour, or two hours, or three hours (etc.) Before midnight on Thursday - and does a calculation that places the amount of hours into a "Standard Pay Rate HOURS Field".

SECOND Calculation Result - I need to create a calculation that takes the timestamped 7-1/2 hours, or 9 hours, or 10-1/4 hours (etc.) AFTER midnight on Friday - and does a calculation that places those amount of hours into a "Shift Pay Rate Hours Field".