[Pharo-project] Alien callback thunk as ExternalAddress?

I am getting near to jumping off the callback cliff. My problem is that I have a generated external structure that expects a void pointer (actually a function pointer). The setter sends #getHandle. I tried to hot-wire that by defining CallbackThunk>>getHandle to answer the #address. Is there a way to get an ExternalAddress that points to the thunk? Should I even be asking this question? :) Bill