It's up and running now.

I couldn't find the error so eventually did what Les suggested and stripped the system down to bare minimum (just a few lines) and succeeded in getting shares to happen.

Then, I slowly cut and pasted code to re-build bit by bit, testing each small change.

I don't THINK the new code is anything substantially different from the original but the new code works! I'm just happy to see it working and can't be bothered to see WHAT was the issue that caused my hassle.

I'm going to pin it to OOLLM! (One of life's little mysteries).

Thanks again for all assistance tendered by the several correspondents.

Best regards from Down Under (Sydney, Australia)
Michael