I downloaded the free Borland Turbo C++ Explorer, brushed up my C - not C++, I don't like very much - which I did not use in may be 20 years, got disoriented by the IDE, had some trouble creating the GUI within the dll but here it is! I am at the same stage as with Delphi but with a big plus: the callback is working.
One side effect: the dll went from 429kB to 37kB. I sill love Delphi and still curious why I did not succeed. Jean-Claude PJ2BVU
