how to get the index of the checked radio button inside a group box?

[saman_artorious]

let's say we have a group box including a few radio buttons. I need to get the index of the clicked or checked radio button so that
I could use it as a parameter to a function, this simplifies my code, you have any idea if that's possible?
if not I need to waste time checking the ischecked() method with if-else