TThread, irgendwas mache ich falsch

[Edelfix]

Sollte eigentlich so funktionieren.

Delphi-Quellcode:

function TMainForm.GetTHTTPClient ( Const xURL : String ) : String;
var
 tmp : String;
 MyThread: TThread;
 TimeOut: Cardinal;
begin
  tmp := '';
  MyThread := TThread.CreateAnonymousThread(
    procedure
    var
     HttpClient: THttpClient;
     HttpResponse: IHttpResponse;
    begin
      tmp := '';
      HttpClient := THTTPClient.Create;
      try
        HttpResponse := HttpClient.Get( xURL );
        tmp := HttpResponse.ContentAsString();
      finally
        HttpClient.Free;
      end;
    end
  );
  MyThread.FreeOnTerminate := True;
  TimeOut := GetTickCount;
  MyThread.Start;
  repeat
    Application.ProcessMessages;
    Sleep(5);
  until (tmp<>'') or ((GetTickCount-TimeOut)>5000); //neu
  Result := tmp;
end;