Let's see. There is C++ and in Visual Studio.NET you can compile it as managed code, meaning that it actually becomes C++.NET code. You should be able to use this in your VB.NET application. Of course, C# is more preferred as a .NET based C-like language because it's easier in syntax and requires a bit less intelligence to use correctly. (It's easier to understand and to read.)

If you can't compile this C code into managed code, then it's still possible to call this code by putting it into a DLL and then build a wrapper around it. Something with P/Invoke's and other complex stuff will be required to be used to access it in that case, though. Pretty complex stuff for the inexperienced developers, though.