Thank you for contacting us.
In order to differentiate the requests from node click and context menu click you could use the ajaxRequest() function. Also you could add a handler for the OnAjaxRequest event of RadAjaxManager. In the handler you could update different controls depending on the event argument.
For your convenience I have prepared a sample project illustrating the approach. Give it a try and let me know if it is working for you.
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 UI for ASP.NET AJAX, subscribe to the blog feed