Hi
Another possibility is that the .NET dlls can be exported as COM objects, and then you could access them as usual. Depends on the 3rd party, I guess.
You could write a .NET wrapper to the 3rd party code that calls the methods you want, and then you can export your wrapper code to COM. I've been doing some of this lately (exporting .NET to COM for 'legacy' apps), so /msg me if it's something you'd want more details on.
HTH, J