Are the radio buttons bound or unbound?
Usually the value you've assigned to the radio button is passed to the frame that contains the buttons, thus one option only is selected. However, it looks to me as though you're using the yes/no, true/false, -1,0 values of the selected/not selected property of the radio button itself. To know which button name to include, you'll have to loop through the form controls and examine the values for controls that are only buttons and retrieve their name if they meet your selected/not selected setting.
EDIT
If the buttons are part of a group, it's easy enough to get the frame value. Based on that, you know which button has been selected, thus it is easier to get its name.
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Paraphrase of Professor Brian Cox.