I have a worksheet that I am figguring commissions on each sale. When a
customer pays by credit card, i have to deduct out of my gross profit margin
2.99% to cover for the Processing fee of the card. What I currently do right
now is calculate that myself, what I would like to do is see if there is a
formula to automatically deduct the 2.99% from the gross profit margin. An
example of what my sheet looks like:
In Column A I have : Date
In Column B I have : Customer Number
In Column C I have : Gross Profit Margin
In Column D I have : Commissions Which right now has this formula in it
=C70*$B$4
In Column E I have : Visa, MC, Terms, AMEX, Discover (Either one depending
upon the card used.)

What I would like to do is if i select any of the credit cards in column E
it would automatically minus 2.99% off of the number in Column C.

Please help me if you can