Can Out of Box (Standard Working Hours) field can be updated automatically by Assigment DFF?

We have a requirement at a school district, where we have a DFF on the assignment page, called Calendar, this field is mapped to a user-defined field that stores the start and end of the school yr, duty days, paid days, and hours per day. The working hours on the assignment is a calculation between the number of paid days times(MULTIPLIED BY) hours per day with frequency as Yearly, Is there any way for this calculation to happen and update the Working Hours on the assignment page based on the selected DFF?