Thanks, Nick and Serenity Now,for your kind remarks and I'm pleased my articles have been helpful.

I know my articles keep popping up long after my retirement from Axiom. This one is heavily edited but it's OK; the important points are retained. In the past, I tended to "write long", so tight editing is often an improvement.

Regards,
Alan

Alan Lofft,
Axiom Resident Expert (Retired)