Bernhard Hiller wrote: Otherwise you should know that C++ does not mean COM! I knew it sounded to easy to me... Bernhard Hiller wrote: If the interface is defined with C++ header files (*.h), then you'll have to write a mixed mode (managed + unmanaged) dll in C++ which in turn can call your VB.Net dll There is a bunch of header files... but I have no idea how to do this "wrapper dll" in c++... also it's neccessary that my dll in turn calls functions of the c++ program (or it's dlls). Would it be possible to do what i want using VB6 instead of vb.net? In the documentation they mentioned (in one sentence) Visual Basic and Delphi as possible languages. I never used VB6 before (stopped using VB at VB3 and restarted with VB.NET 2010) but i think that will be much easier for me than learning C++ from scratch. Anyway thanks for your answer Bernhard... even if I'm not really happy with my new knowledge ;)