How to add up pay based on several entered factors

How to add up pay based on several entered factors

I need help entering Driver Pay and Dispatcher Pay based on their pay rate and load amount. I have a "Contacts" form where the driver and dispatcher name and pay % live, and a "Loads" form where the load information, load pay, driver is selected and dispatcher is selected (Lookups).

Example:
Form: Contacts -> Dispatcher John Doe
Field: Pay %: 3%

Form: Contacts -> Driver Chris Smith
Field: Pay % -> 25%

Form: Loads
Field: Load Pay -> $1,000

Form: Loads
Field: Dispatcher Pay ->  ???? (to be calculated automatically and displayed based on load pay multiplied by dispatcher pay %)
Field: Driver Pay ->  ???? (to be calculated automatically and displayed based on load pay multiplied by driver pay %)

Thank you!!!!