MS Access 2007 – Deselecting an Option Group on Forms

I have a form where the user enters a dollar amount in one field and then selects from an option group to identify what the amount is for. The form works fine for entering the amount and selecting the matching option. The problem is that I cannot figure out how to “uncheck” the option selected when the user enters an amount and has to undo their entry. For the dollar amount they just enter $0 but there is no way for them to uncheck from the option group. I prefer not to use code but if you want to send me the script I can usually figure it out.