Currently both the RadChart and the HTML Chart does not provide this feature. However the HTML Chart has significantly better layout engine, which I believe should better work in your scenario. I have attached a sample project with it.
If you have any further questions, I'll be glad to help.
the Telerik team
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 their blog feed