When you add a radio button to a form, you are prompted as to how many you
would like to add. The amount of buttons is then automatically added for you
to the form. If you want to add an additional radio button afterwards, you
can drag and drop a radio button onto the form, change its binding to the
same Data Source field as the other radio buttons, and change its "Value when
selected" (on the Properties dialog box for the radio button) to the value of
the last radio button plus 1 (so if you had 4 radio buttons on a form and
then added an additional one, the "Value when selected" of the new radio
button should be 5).
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S.Y.M. Wong-A-Ton

Hi even I am facing the same problem. Any solution ?
To explain it :
I have a repeating section. In this section there is a table of one row.Now
the first column is a radio button. Since this is a repeating section so I do
not know the no. of rows that can be at a time. I want the user to select a
row by clicking on the radio button (first column). But since the radio
buttons cannot be grouped here. I want to user to select only one radio
button at a time. Is there any way I can acheive the grouping of the radio
buttons in this scenario ?
Thanks in advance