If this is not what you want, I recommend to implement the desired logic not by using RadWindow, but a standard browser's popup (window.open()) or an IFRAME (RadWindow is basically an IFRAME). Once you have your logic working as expected, the same approach will work with RadWindow as well.
If your code is working fine with popup / IFRAME but you experience problems converting it to use RadWindow, open a support ticket and send us the working project. We will check it and rework it for you.
the Telerik team