For this purpose you can use the RadToolBarButton
and set the CheckOnClick="true"
of the button. Thus, you can check as many buttons as needed. Please take a look at our on-line demo for more information and an example - RadToolBar - Telerik's ASP.NET ToolBar
If you want to get updates on new releases, tips and tricks and sneak peeks at our product labs directly from the developers working on the RadControls for ASP.NET AJAX, subscribe to the blog feed