TScrollBox响应鼠标滚轮问题

Delphi的TScrollBox本身并不响应鼠标滚轮事件(不知道为什么)，但可以在ScrollBox的鼠标滚动事件中进行控制：

procedure TfrmTaskNoteEdit.ScrollBox1MouseWheel(Sender: TObject; Shift: TShiftState; WheelDelta: Integer;
  MousePos: TPoint; var Handled: Boolean);
begin
  if   WheelDelta   <   0   then
    SendMessage(scrollBox1.Handle,WM_VSCROLL,   SB_LINEDOWN,   0) //向下滚
  else
    SendMessage(scrollBox1.Handle,WM_VSCROLL,   SB_LINEUP,   0); //向上滚
end;

测试通过，奇怪的是我在一个PageControl的两个页面中分别放置两个ScrollBox时只有一个有响应，郁闷，后来只好调整到窗体的MouseWheel事件中：

procedure TfrmTaskNoteEdit.FormMouseWheel(Sender: TObject; Shift: TShiftState; WheelDelta: Integer; MousePos: TPoint;
  var Handled: Boolean);
begin
  inherited;
  case RzPageControl1.ActivePageIndex of
    0:
    begin
      if WheelDelta < 0 then
        ScrollBox1.Perform(WM_VSCROLL,SB_LINEDOWN,0)
      else
        ScrollBox1.Perform(WM_VSCROLL,SB_LINEUP,0);
    end;
    2:
    begin
      if WheelDelta < 0 then
        ScrollBox2.Perform(WM_VSCROLL,SB_LINEDOWN,0)
      else
        ScrollBox2.Perform(WM_VSCROLL,SB_LINEUP,0);
    end;
  end;
end;