When a selection is made
To determine which Radio Button Set is selected, make an event-to-script connection from the selectedItemChanged event of the Radio Button Set part to a script. 
For example, the following code fragment sets the proper sampling rate record setting for a music recorder based on the Radio Button Set in the Sampling Rate group: 
    (self subpartNamed: #musicPlayer)
        setSamplingRate: (#(8 11 22 44)
           atIndex: selectionIndex)
Note:
The indexing of the Radio Button Set is 1-based, not zero based. 
Last modified date: 01/29/2015