Shift differential option under daily overtime

This option is unique to me but may be to other fields of jobs. If I work more than 12 hours in a day I get “shift differential” which is a seperate per hour wage for the entirety of that shift in addition to my regular/over time hours. For example a 12 hour shift would get me 10 hours straight pay, 2 hours overtime pay and 12 hours shift differential at $x/hr. Right now I calculate it myself and put it in the bonuses option for that shift but it would be nice as an auto calculator option.

Thank you