When I execute the (2nd) below code with a wrong url (number '1' added at the URL end), I get the below error. How can I catch this error, in case the url is wrong, so that I can give out an error message to the user ?

Error opening URL 'http://localhost/myapp/cgi-bin/savePlanScale.ashx1?NoCache%5FRaumplaner=F7CF6A1E%2D7700%2D8E33%2D4B18%2D004114DEB39F&ScaleString=5%2E3&ModifyFile=data%2Fdata%5Fzimmere03e1e83%2D94aa%2D488b%2D9323%2Dd4c2e8195571%2Exml' httpStatusHandler: [HTTPStatusEvent type="httpStatus" bubbles=false cancelable=false eventPhase=2 status=404] status: 404 Error: Error #2101: Der an URLVariables.decode() übergebene String muss ein URL-kodierter Abfrage-String mit Name/Wert-Paaren sein. at Error$/throwError() at flash.net::URLVariables/decode() at flash.net::URLVariables() at flash.net::URLLoader/onComplete()

    public static function NotifyASPXofNewScale(nScale:Number)
{
   var strURL:String ="http://localhost/myapp/cgi-bin/savePlanScale.ashx1"
   // CAUTION: when called from website, RELATIVE url...
    var scriptRequest:URLRequest = new URLRequest(strURL);
   var scriptLoader:URLLoader = new URLLoader();
   // loader.dataFormat = URLLoaderDataFormat.TEXT; // default, returns as string
   scriptLoader.dataFormat = URLLoaderDataFormat.VARIABLES; // returns URL variables
   // loader.dataFormat = URLLoaderDataFormat.BINARY; // to load in images, xml files, and swf instead of the normal methods
   var scriptVars:URLVariables = new URLVariables();

   scriptLoader.addEventListener(Event.COMPLETE, onLoadSuccessful);
   scriptLoader.addEventListener(IOErrorEvent.IO_ERROR, onLoadError);
   scriptLoader.addEventListener(HTTPStatusEvent.HTTP_STATUS, httpStatusHandler);
   scriptLoader.addEventListener(SecurityErrorEvent.SECURITY_ERROR, onSecurityError);

   scriptVars.NoCache_Raumplaner = cGUID.create();
   scriptVars.ScaleString = nScale;
   scriptVars.ModifyFile = "data/data_zimmere03e1e83-94aa-488b-9323-d4c2e8195571.xml";

   scriptRequest.method = URLRequestMethod.GET;
   scriptRequest.data = scriptVars;

   scriptLoader.load(scriptRequest);


   function httpStatusHandler(event:HTTPStatusEvent):void 
   {
        trace("httpStatusHandler: " + event);
        trace("status: " + event.status);
    }

   function onLoadSuccessful(evt:Event):void
   {
        trace("cSaveData.NotifyASPXofNewScale.onLoadSuccessful");
        trace("Response: " + evt.target.data);


        ExternalInterface.call("alert", "Die neue Skalierung wurde erfolgreich gespeichert.");
        //getURL("javascript:alert(\""+"Die neue Skalierung wurde erfolgreich gespeichert.\\nALLE Instanzen des Browsers schliessen und neu starten, damit die Änderung in Kraft tritt."+"\");");

        if (evt.target.data.responseStatus == "YOUR FAULT")
        {
            trace("Error: Flash transmitted an illegal scale value.");
            ExternalInterface.call("alert", "Fehler: Flash konnte die neue Skalierung nicht abspeichern.");
        }

        if (evt.target.data.responseStatus == "EXCEPTION")
        {
            trace("Exception in ASP.NET: " + evt.target.data.strError);
            ExternalInterface.call("alert", "Exception in ASP.NET: " + evt.target.data.strError);
        }
       }


       function onLoadError(evt:IOErrorEvent):void
       {
       trace("cSaveData.NotifyASPXofNewScale.onLoadError");
       trace("Error: ASPX or Transmission error. ASPX responseStatus: " + evt);
       ExternalInterface.call("alert", "ASPX - oder Übertragungsfehler.\\nASPX responseStatus: " + evt);
       //getURL("javascript:alert(\"" + "ASPX - oder Übertragungsfehler.\\nASPX responseStatus: " + receiveVars.responseStatus + "\");");
   }


   function onSecurityError(evt:SecurityErrorEvent):void
   {
        trace("cSaveData.NotifyASPXofNewScale.onSecurityError");
        trace("Security error: " + evt);
        ExternalInterface.call("alert", "Sicherheitsfehler. Beschreibung: " + evt);
   }

   }