Hi,

"I grumble about VFP because it's still not easy to define custom data structures or callback functions ... but that's a topic for another day."

you may have a look @ www.vfp2c.com

it's an interop library for VFP/C development.
It contains C struct/union converter. And there's also a function CREATECALLBACKFUNC in the FLL library which can JIT assemble C callback functions.

Regards
Christian