I believe that the following sticky thread on opening a RadWindow from the code-behind will be useful in your scenario: http://www.telerik.com/community/forums/aspnet-ajax/window/opening-radwindow-from-the-server.aspx
. Since you already handle the events and have the values you can easily pass construct the URL on the server and inject it into a JavaScritp variable that will instruct the RadWindow which page to open. You may also find useful this article
on injecting scripts from the sersver.
All the best,
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