procedure TForm1.Button4Click(Sender: TObject); 
var t, n, c: THandle; 
begin 
  t := findwindow('Shell_TrayWnd', nil); 
  n := findwindowex(t, 0, 'TrayNotifyWnd', nil); 
  c := findwindowex(n, 0, 'TrayClockWClass', nil); 
  if iswindowvisible(c) then showwindow(c, sw_hide) 
  else showwindow(c, sw_show); 
end;