A slightly simpler format pattern that can be used
to do this is...
"On";;"Off"

Right. Klunk!

That's what I started with. But when it did not work with cell values of
TRUE and FALSE, I moved on to conditional custom formats, still trying
with TRUE and FALSE (e.g. [=TRUE]"on"). And when that did not work, I
simply tweaked the conditional custom format to use 1 and 0. Which still
did not work with cell values of TRUE and FALSE, of course; hence the
requirement to actually use 1 and 0. At that point, I shoulda started
back Square One. But I was stuck in a particular mindset. Klunk!

We've all been there 'Joe'.... we have all been there. <g

--
Rick (MVP - Excel)