I've created a formula field to calculate Commission payable on a Potential , this portion works find.

(${Potentials.Amount}*0.05)+
(${Potentials.Year 2 Expected Revenue}*0.02)+
(${Potentials.Year 3 Expected Revenue}*0.02)

However when I try to add a 'IF' condition to calculate a final piece I get an error message that I do not understand. See full formula with problem piece in bold.

(${Potentials.Amount}*0.05)+
(${Potentials.Year 2 Expected Revenue}*0.02)+
(${Potentials.Year 3 Expected Revenue}*0.02)+
(If(${Potentials.Paid In Advance}==TRUE,${Potentials.Amount}*0.01,0))

Here is the error message " You used the wrong type of data in an argument. Check what you entered between the parentheses of your functions to make sure you put the right kind of data in the right place."

Any help would be greatly appreciated.

Regards, Roger