Where can I find out more information on the HTML Help API?
Full documentation is located in the HTML Help Workshop help files. Unfortunately, they’re geared toward C/C++ programmers. On the other hand, Dan Appleman’s Visual Basic 5 Programmer’s Guide To The Win32API contains instructions on how to convert this type of code for use in Visual Basic. I highly recommend this book, or its successors, if you’re going to use the API at all in Visual Basic.