Help needed creating calculations for a timesheet on adobe!

I have made the hours add up in the total hours box at the bottom. Not sure how to code or make the regular hours equal what they need to be or the overtime hours box what it needs to be.

Essentially the total hours box is just a running sum of all hours worked (super easy).

The "regular hours worked" box needs to be a running sum up to 86 hours but no more than 86, and the overtime hours box needs to be the difference of total hours and regular hours, or anything over 86 if that makes sence.

The current names for the fields are "regularhours" "allhours" and "overtime". 

Any help creating this or teaching this to me would be greatly appreciated!!!