Как глобально перехватить нажатие кнопки PrintScreen?

Code:

type

              TForm1 = class(TForm)

                procedure FormCreate(Sender: TObject);

                procedure FormDestroy(Sender: TObject);

              private

                { Private declarations }

                procedure WMHotKey(var Msg : TWMHotKey); message WM_HOTKEY;

              public

                { Public declarations }

              end;

            var

              Form1: TForm1;

            implementation

            {$R *.DFM}

            const id_SnapShot = 101;

            procedure TForm1.WMHotKey (var Msg : TWMHotKey);

            begin

              if Msg.HotKey = id_SnapShot then

                ShowMessage('GotIt');

            end;

            procedure TForm1.FormCreate(Sender: TObject);

            begin

              RegisterHotKey(Form1.Handle,

                             id_SnapShot,

                             0,

                             VK_SNAPSHOT);

            end;

            procedure TForm1.FormDestroy(Sender: TObject);

            begin

              UnRegisterHotKey (Form1.Handle, id_SnapShot);

            end;