它能利用lostFocus事件过程对输入的内存大小进行合法性检查，确保最后两个字符是“MB”，其余的都是数字字符。当用户单击“OK”按钮后，在右边的文本框中显示所选择的信息-It can use lostFocus event procedure for the memory size of the input validation, ensure that the final two characters are " MB" , the rest are numeric cha