KeyKit is its own language, it can't be used directly from within C/C++/VB. I had it working directly from within Python at one point, but that's not an appropriate method to pursue. You can, however, interact with KeyKit from other languages (or other computers) by setting up a socket connection - OSC being the easiest protocol to get working. You can also use Midi Yoke (on Windows) to send MIDI data directly between programs written in different languages. I routinely use KeyKit in this mode, combining it with programs written in C/C++/Python.
...Tim...