Ok, thanks for clarification.

I still have trouble with getting the right results. The GetHeartCoherence function returns a long and the DLL returns always 123 in my VC++ app (because this is a debug version for me), but in Lite-C I get a 2 - and 123 is confirmed by the developer that this is the right return value.

Can you imagine why this could happen?

Not without knowing more of that DLL. If you get a 2, I'd suspect you called a wrong function, as the 2 could be the return value of AddRef. Make sure that your Vtbl contains the same functions in the same order and with the same types as in the orginal DLL; the 3 standard methods must be at the start. If some type is not supported by lite-C, find an equivalent of the same size - usually a long or void* works for everything.

If the class inherits something, be sure to add the inherited methods directly after the 3 standard methods, followed by the specific methods of the class. See the example in the manual.