Jason Morin wrote...
Yes, simply returning a TRUE or FALSE occurred to me. But
if you're sharing the worksheet with others, such as a
boss, it's more time-consuming to explain TRUE or FALSE
then "Formula" and "".
....

The prototypical pointy-haired boss who doesn't understand the
explanations? Now, since you named the formula IsFormula, and since
there are several built-in functions (in English language versions)
beginning with IS that return True/False, just how pig-headed do you
believe these co-workers are?

Silly me believing that semantic consistency with similarly named,
similarly used built-in functions would cause less trouble in the long
run.