Where a group of buttons is inter-related, the following code should
do:
set(handles.option1, 'Value', 1);
set(handles.option2, 'Value', 0);
set(handles.option3, 'Value', 0);
where option1 is the source of the callback. For the other
options, the only part which needs changing is the latter one where
the state of the button is defined by a zero or a one.
