用vb编写的3个带有导出函数的dll，给出了相应的调用代码。用vb编写和调用dll时有一些限制，涉及到BSTR/VARIANT类型的函数最好用vc编写成dll/com。 -Prepared using vb export functions with three of the dll, call the corresponding code. Using vb to prepare and when to call dll has some limitations related to BSTR