A group of radio buttons (a group of buttons of which only one at a time can be selected) is created with the
radio-button-panel
class. Here is an example of a radio button panel:
(setq radio (make-instance 'radio-button-panel
:items (list 1 2 3 4 5)
:selection-callback 'test-callback))
(contain radio)
Figure 5.2 A radio button panel