datagrid 如何实现鼠标滚动翻页

procedure Tfrmsetcrop.ApplicationEvents1Message(var Msg: tagMSG;
  var Handled: Boolean);

begin
  inherited;
 if (DBGrid1.Focused) And (Msg.message = WM_MOUSEWHEEL) then
    begin
      if Msg.wParam > 0 then
        SendMessage(DBGrid1.Handle, WM_KEYDOWN, VK_UP, 0)
      else
        SendMessage(DBGrid1.Handle, WM_KEYDOWN, VK_DOWN, 0);
      Handled := True;
    end;