type
  TCheckBox = class(VCL.StdCtrls.TCheckBox)
    procedure CNCommand(var Message: TWMCommand); message CN_COMMAND;
  end;

{ TCheckBox }

procedure TCheckBox.CNCommand(var Message: TWMCommand);
begin
//   inherited;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  SetWindowLong(CheckBox1.Handle, GWL_STYLE,
    GetWindowLong(CheckBox1.Handle, GWL_STYLE) or BS_PUSHLIKE);
end;