SDL Tridion 2009 SP1 Custom URL Gets Current Field Value

I am connecting to a custom url in the component field that contains the following code

        function SaveAndClose()
        {
            var newValue = new Array();
            newValue[0] = "/feed.ashx?type="+ $("#Type").val() + "&user="+ $("#User").val();
            window.returnValue = newValue;
            self.close();
        }
       document.write("Current Value:");
       document.write(window.dialogArguments.fieldValue);

The SaveAndClose function works fine and sends the value back to the component, but window.dialogArguments.fieldValue always returns undefined.