I've written a tutorial on using C++ for blending colors, it's somewhat VB-friendly. Read it and let me know what you think! The code is totally usable, so you could copy it directly from the article, add the necessary export settings, and make it a DLL to use in your VB apps!
I've submitted it to gamedev.net for review and possibly posting, so i'd love to get your feedback too!
It's almost the exact same technique i use in my library, so it's fast.
If I get enough response to this article, i'll write another covering blitters and more effects.