Load default image if 'URL Not Found'

Hey there, I’ve got a slideshow which runs from an XML file, and at the moment, if the image specified in the XML file isn’t there, I get an error

Error #2044: Unhandled IOErrorEvent:. text=Error #2035: URL Not Found.

and here is the function which loads the image:

private function Load_thumbnail():void
            for (var i:uint = 0; i<numphot; i++)
                var myLoader:Loader = new Loader();
                var myRequest:URLRequest = new URLRequest(thumb*);
                myLoader.contentLoaderInfo.addEventListener(Event.COMPLETE, Thumb_loaded);
                pInfor[myLoader] = i;

What I want to do is load a default .jpg if the URL is not found, I have no idea of how to go about this, so any help would be gratefully appreciated…