the provided link really helped me because in my case i need to prevent the custom validator to fire twice.
in princy case the flag will change its status if we close the window but if it is still display then we would get more than one window displayed.
but the other link can give me a reference to the displayed window as mentioned below
var oAlert = radalert(text, oWidth, oHeight, oTitle, callbackFn, imgUrl);
This method also returns a reference to the RadAlert object (which is essentially a RadWindow), so you can use the
RadWindow's client-side API on it to further change it (titlebar icon, behaviors, etc.)
so from oAlert i can use IsClosed() function to check if the window still display or not
thanks very much guys for helping, i really appreciate it.