怎么用鼠标滚动来控制DBGRID移动？

自己捕捉WM_MOUSEWHEEL消息处理
private
 OldGridWnd : TWndMethod;
procedure NewGridWnd (var Message : TMessage);
public

procedure TForm1.NewGridWnd(var Message: TMessage);
var
 IsNeg : Boolean;
begin
 if Message.Msg = WM_MOUSEWHEEL then
 begin
   IsNeg := Short(Message.WParamHi) < 0;
   if IsNeg then
     DBGrid1.DataSource.DataSet.MoveBy(1)
   else
     DBGrid1.DataSource.DataSet.MoveBy(-1)
 end
 else
   OldGridWnd(Message);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
 OldGridWnd := DBGrid1.WindowProc ;
 DBGrid1.WindowProc := NewGridWnd;
end;