Trigger update panel from JavaScript

I have a Telerik Treeview OUTSIDE an update panel, and would like to trigger an asynch postback in the update panel and pass in parameters from the Treeview.

It is easy enough for me to capture the click event in JavaScript, including all node values.

The trick is:

How do I trigger the update panel and pass in those parameters from JavaScript?

Look here:

http://forums.asp.net/thread/1541012.aspx