Add a template specific page class per style

I have a T3 template installed on my site. I'm using two sub version of the template for specific menu items. So in the backend I have three template styles.

What I would like to do is add a template specific class to either the or tag so I can assign CSS to those specific pages displaying the template.

I would rather do it this way than add a page class to every menu item.

Can this be done via php in the tpls files?

Thanks

Lee