"how about VB + C application?"

That'd be pointless!
Just throw away the VB and use MSVC, BCB, Delphi or any of the other so-called "RAD" [1] products based on "proper" languages!

"The problem most often faced with C is in providing a GUI"

That's precisely what the 'V' in MSVC gives you - and it's also the raison d'etre of the others!
(which is, unfortunately, why you can't write embedded stuff with BCB :-( )

Unless you have some external constraint to use it, I can't see any reason to do so.

[1] RAD = Rapid Application Development