Need Help with an Excel Formula

Good afternoon Folks. I need some help with a excel formula.

I need the formula for finding the difference between two values and if the difference is larger add that difference to the constant

Example B1 is a constant, when E1 is >C1 add the difference to B1 in F1

B1= 500 E1= 1000 if C1 is greater than E1 that difference is is added to the B1 constant in F1 if not F1 = B1

Cell:
B1 Constant is base salary.
C1 Is a running total for the salary paid.
E1 Is the running total of commissions.
F1 Is the sum of the constant Salary & the different between running total of Salary and total commissions.



Please help

Thank You,
Job