This is a pretty straightforward question, I am just not sure if it is possible with the GF merge tags.. in essence it is an if statement, which I know GF doesn't do but maybe it is still possible.
Essentially I want to do a price calculation, based on a checkbox product price field for the default value, soo basically:
calculation = {field default} - {field value}
So if I have a checkbox field for +$20 the calculation would be $20 - $20 if checked, $20 - 0 if not checked...
possible?