自定义函数是指利用VBA编写的外置函数。在本例的随书光盘中已经录入了相关的VBA代码，可以随时调用。对于代码的含义和录入方式在后面的章节后有详细介绍，本章仅通过具体应用了解其用法与优势。-Custom function refers to the use of external functions written in VBA. In this example, the CD with the book has been entered