Most efficient way of showing 'pressed' state of buttons in an XML men

Ok, that’s not a great title. Let me explain.

I quite often have to create portfolio sites which have a list of projects on the lefthand side. When each project is clicked the relevent content is loaded into the main screen. I’m now moving towards creating such sites where the menu content is XML driven.

What I want to know is, what is the BEST way to do the old radio button style thing where the clicked button changes state (eg. colour) and the when another button is clicked, it returns to it’s up state.

I’ve done this before, when I’ve created the buttons manually, by creating a ‘clicked’ variable that can either be true or false for each button, the value of which is changed when a button is clicked. The problem with this (I think) is that it relies upon me knowing how many buttons I have, and if this is driven by XML that is going to get messy.

What I’m after is a very simple, self contained method of setting a button’s state when it is clicked (no problem), but then ‘unclicks’ when any other button in the menu is pressed.

Hope this makes sense!

Thanks in advance!