function StartDFUE(NameDerVerbindung: string): boolean; 
begin 
  result := 
    shellexecute(application.handle, 'open', 'rundll32.exe', 
      pchar('rnaui.dll,RnaDial ' + 
    NameDerVerbindung), nil, sw_show) > 32; 
end; 
 
procedure TForm1.Button1Click(Sender: TObject); 
begin 
  if not startDFUE('Mobilcom') then showmessage('Fehler'); 
end;