张继春老师的二次开发书中关于VB进行二次开发的例子，一共四个程序，有齿轮的参数化，特征选择和尺寸显示等内容。-ZHANG Jichun Teacher of the secondary development of a second book about the development of VB example, a total of four procedures, there is gear parametric, feature selection and size of display