type
   TForm1 = class(TForm);
   // ..
  private
     procedure WMSysCommand(var message: TWMSysCommand);
       message WM_SYSCOMMAND;
   // ..
  end;
 
 implementation
 
 const
   idMyFunc = $f200;
 
 procedure TForm1.WMSysCommand(var message: TWMSysCommand);
 begin
   inherited;
   if message.CmdType and $FFF0 = idMyFunc then
     ShowMessage('my new function');
 end;
 
 procedure TForm1.FormCreate(Sender: TObject);
 begin
   AppendMenu(GetSystemMenu(Handle, False), MF_STRING, idMyFunc, 'Info');
 end;