The main points in such approach are:
property. You can use this fact, to build the logic that will limit the total number of RadWindows that can be opened.
2. While inside a content page that is shown in a RadWIndow, you can get a reference to that RadWindow, by using the GetRadWindow() function. Once you have access to the RadWIndow object, you can get the parent page as well, by using the BrowserWIndow property from RadWindow's API. From this point on, just get the location.href property of the parent window, and you'll get its Url
oWnd = GetRadWindow();
parentPage = oWnd.BrowserWindow;
I created a simple demo that you can use as a base for your implementation. In it, I limit the maximum number of opened RadWindows to 5 and I get the parent page's Url by using the function shown above.
Please check the demo's code for more details.
the Telerik team