Changing colour when duplicate record

[bruceR]

Adding to what comment said, there are a number of things that cause conditional formatting calcs to re-evaluate.

"Oooh, did the user resize the window? Or modify data? Or... ? Better run through all these formatting calcs again!" That's what the little conditional formatting gnome is thinking to himself.

Edited June 18, 2015 by BruceR

[Andeye]

Thanks Comment & Bruce.  Yes, it all makes sense now.  

I'll just move to unique-value validation with override rather than reinventing the wheel.  Thanks for all your help.