Generally, I would advise on posting unrelated questions in separate threads to make each discussion more concise.
On the exact issue at hand - without having any concrete information on the matter I can only make several suggestions:
- if you are using RadHtmlChart - the OnClientSeriesClicked client-side event
- if you are using RadChart examine this help article
on working with its server side events and this one
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