数据窗口的错误提示不显示（item '' does not pass validation test!）
在ItemChanged中Return codes:
0 - (Default) Accept the data value
1 - Reject the data value and do not allow focus to change
2 - Reject the data value but allow the focus to change
messagebox()
return 1
在ItemError中Return codes:
0 - (Default) Reject the data value and show an error message box.
1 - Reject the data value with no message box.
2 - Accept the data value.
3 - Reject the data value but allow focus to change.
return 1