I have a RadWindow, in that rad window there is a button that will popup another radwindow. (Inside the parent window,and it is a different page). I should be able to send my datatable to Parent radwindow after closing the child radwindow. Any suggestions?
This greatly depends on your setup and the data you need to pass. Here is a brief overview:
you have a server object and you cannot pass the data through JavaScript: Devise a way to store the data on the server (e.g., in the Cache or Session) so you can access it later in the parent page.
You can pass the data via JavaScript: In this case you can simply handle the RadWIndow's OnClientClose event to get the data and pass it to its close() method from the content page, as shown here: http://www.telerik.com/help/aspnet-ajax/window-client-side-events-onclientclose.html.
In either case, you should use the OnCLientClose event to either work with your data on the client (see this demo http://demos.telerik.com/aspnet-ajax/window/examples/dialogreturnvalue/defaultcs.aspx), or to initiate a postback on the first dialog that will work with the data on the server.
This demo will show you a slightly different way of going through the server and then performing an AJAX request to update the first page: http://demos.telerik.com/aspnet-ajax/controls/examples/integration/gridandwindow/defaultcs.aspx?product=window.