[glade--]radiobutton "clicked" signal handler

Hi, 

I hope that this list is right list to ask this question. I am using
glademm 0.6.4 (Gnome Glade 0.6.4). I have looked through the GTKmm 
tutorial documentation but have been unable to find this info. 

I have several radiobuttons (Gtk::RadioButton) in my GUI which all have 
signal handlers for the "clicked" signal. 

Scenario:
RadioButton A is active (selected).
RadioButton B is clicked.

Then, the signal handler for A is called and then the signal handler for B 
is called. 

Questions:

1. I would like only B's signal handler called when B is clicked. I don't
want to have the signal handler for A called. How can I do this?

2. Alternatively, From within the radio-button's signal handler function,
how do I tell if the radio button is being "checked" or "unchecked"? If I 
know this, then I can execute the code when a button is "checked". 

3. How do I find out which radio-button is active from main() or from any 
other signal handler? 

4. Is it possible to have a Gtk::Button which is round (circular) in
shape? 

I would appreciate any advice/suggestions. 


Thanks,
Sajjad