Como desabilitar o fechamento do form?

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;