How to call a C++ dll function at runtime ?

[Igor Vartanov]

I want to give an application interface away for free, then charge for modular updates.

Then your approach of native exporting C++ class is wrong. What you need is "expose a needed subset of class functions as interface". Of course additionally you'll need some API for object creation/destruction, like Paul already said. The technique is really mature and proven to be safe and effective. With certain effort your dll becomes even cross language compatible and this way installable in third party apps, letting you reach clients beyond C++. As I mentioned, most of plugins go this way.