Changing a field value based on another field?

I have a form with a calculated field. The field calculates a value based on number of team entered. (so if you have 16 teams, the amount owing is $1600). A straight-forward calculation.

I need to pro-rate the value based on whether the team is in for a full season or a half season. Since I can't do a calculation based on a radio button field, I'd like to do the calculation based on a hidden number field, but change the value of the number field based on the selection of the radio button.

So, if the user selects "Full Year" in the radio button, it would send that value (1) to the hidden number field. If they select "Half Year", it would send that value (.5) to the hidden number field. Then I'd do the calculaton based on the hidden number field.

Is this possible?

Never mind. I figured out how to do it.

Instead of using a radio button, I used a select field, and was able to do the calculation directly instead of my proposed workaround.