This code in the implementation of a marshaler class returns the handle of the PBX:

extern pbulong thisModuleHandle;
pbulong SampleMarshaler::GetModuleHandle()
{
   return thisModuleHandle;
}

The handle is set in the main module:

pbulong thisModuleHandle = 0;
 
BOOL APIENTRY DllMain( HANDLE hModule,
                       DWORD  ul_reason_for_call,
                       LPVOID lpReserved
                )
{
   thisModuleHandle = (pbulong)hModule;
 
    switch (ul_reason_for_call)
   {
      case DLL_PROCESS_ATTACH:
      case DLL_THREAD_ATTACH:
      case DLL_THREAD_DETACH:
      case DLL_PROCESS_DETACH:
         break;
    }
    return TRUE;
}