In VB, it is not difficult Twofish, Blowfish, RSA, etc., etc., instead. There is plenty of classroom modules. Also, the speed is good. And if you have large files to encrypt 2gig want, but you can still C + + DLLs ...
But the other side is just why reinvent the wheel ...
There are so many good encryption programs that are for private use are more than adequate. For example, Moose Crypt, or the widespread PGP.
In relation to the Crypto API:
Trust never MS (at least I do not). Use better algorithms and libraries, which are transparent. The security guarantees may be (myself read that the Algos be quite good), but I would like to use them only reluctantly ...
To participate in the source code for each, easy to actuate Google with the keywords "VB + Crypto."
That should actually suffice ...