Open RadWindow from Javascript?

[Clive Hoggar]

This should be simple but I am getting an error 'oWnd is Null' in Firefox error console when the function is called
The context is an asp.net vb child page which uses a masterpage containing the Script Manager.

Can someone put me out of my misery?

The window is simply

<telerik:RadWindow ID="RadWindow1" runat="server">
   </telerik:RadWindow>

and the javascript is 

<script type="text/javascript">
        function UseRadWindow() {
            var oWnd = $find("<%= RadWindow1.ClientID %>");
            oWnd.show();
            oWnd.setSize(400, 400);
            oWnd.setUrl("http://www.yahoo.com");
            oWnd.minimize();
            oWnd.maximize();
            oWnd.restore();
        }
   </script>

[Clive Hoggar]

Acting on a hunch I changed 'RegisterWithScriptManager' to false in the window properties...
It now works. Not sure why!

[Kevin]

Hello Clive,

When do you call the UseRadWindow function? Is it during the page load?