Como desabilitar as teclas Alt + F4

public

  { Public declarations }

  fecha: Boolean;

  end;

 implementation

 {$R *.DFM}

Function GetStateK (Key: integer): boolean;

begin

  Result := Odd (GetKeyState (Key));

end;

procedure Tfrm_HIP.FormClose(Sender: TObject; var Action: TCloseAction);

begin

If Not fecha Then

  Action := caNone 

Else

  Action := caFree;

end;

procedure Tfrm_HIP.FormKeyDown(Sender: TObject; var Key: Word;

Shift: TShiftState);

begin

   If GetStateK (VK_LMENU) And (Key = VK_F4) Then

      fecha := False;

end;