All the bookshops and libraries I've been too have never stocked anything decent on the programming front apart from one university bookshop (happened to have a dedicated Computer Science facility on-site and its a major course there) and even then it was quite limited but they can't stock everything. Your best bet is to get books via
Amazon even though it would appear that they don't have a dedicated service for Africa (but I'd guess ship to there), a good book I have on C++ is
C++: The Complete Reference fourth edition by Herbert Schildt, ISBN-978-0072226805 which is all you'll need on that front. I found with Visual Basic.NET that
MSDN and general tutorials on the net were all I needed to get to grips with VB.NET so I don't have any recommendations for books on it so if you really feel like reading up on it you can search around on Amazon.
VB.NET is easy to get results from and learn so if you want another language like that you could try JAVA which is quite popular at universities at least in the first year, which if you're planning on attending one for a Computer Science course would be handy to know.
Also a note on the book front, you can usually find .PDF or .CHM versions of books on
torrents if you are inclined towards warez, not that I would condone such a thing of course...