[lazarus] Menu problem

[jozsef at wingchun.hu]

Hello,

procedure TForm1.popclick(Sender:TObject);
begin
  (Sender as TMenuitem).Checked:= not (Sender as TMenuItem).Checked;
end;

This code checks in properly but never checks out.
I'd like a radiolike thing. Only one can checked.
Do you know a solution? Share with me, please. :)
(I use popupmenu of course.)

Joe