sorry I have been post and instead of OR as you ask so

=or(iserror(b1),iserror(c1))

regards
Marcelo

"luvthavodka" escreveu:

How can I set the conditional formatting of a A1 if B1 or C1 shows #n/a?

(B1 and C1 both contain formulae that will return #n/a until the required
information is inputted elsewhere in the spreadsheet. Hence I want
conditional formatting to highlight information that is missing)