If you're asking about passing a parameter to a form, the simplest is most likely to use a request parameter. Then, in your form, you can use xxf:get-request-parameter('my-param') to access the value of the parameter, for instance to set the initial value of a control.
http://wiki.orbeon.com/forms/doc/developer-guide/xforms-xpath-functions#TOC-xxforms:get-request-parameter-It also seems that you would like to have the label of the control be dynamic, which is not supported out of the box by Form Builder. Even if not ideal, you could maybe simulates that by using an output control next to the radio box.
Alex
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