If you are forced to use native C++, you have to use COM Interop, indeed.
Here is how you can do this:

  tlbExp myVBdotNETLib.dll

generates a .tlb file

in your C++ code:
 #import "myVBdotNETLib.tlb"

However if you can use the managed features of C++, it is much easier, since
you just need to reference the managed dll in order to use it's types from
managed code. You can import this either via
#using "myVBdoNETLib.dll"
or via the compiler switch /FU, use VS.NET project settings for that.

Marcus Heege