Rod Gill has put out a new book which covers most of what you need for Microsoft Project VBA programming. As far as I know it is the only book about VBA that I know of. The last edition of Tim Pyron's "Using Microsoft Project" was so full that the VBA chapters were moved to an addendum on the web so it is great to see a book dedicated to just VBA. The book moves from the most basic concepts through creating some useful macros and userforms. It even offers an updated version of something very similar to my "Trace" macro. At the end of each chapter there are some example questions/problems which would make this book very useful if you are teaching VBA in a class. In the US the book was localized by Gary Chefetz and Dale Howard of MSProjectExperts and if you are familiar with their Project Server books you will be happy to see that the same high quality is embodied here. Highly recommended for anyone who wants a solid grounding in Microsoft Project VBA. Here is a link to the book at Amazon.
While you are at it check out Gary and Dale's Project Server Books:
Disclaimer: I know these guys and have had dinner with them at least once.