> "More work for the buffs, what is the formula to convert a 1 in column A to a 0 in column B and visa versa?"

Have either of the preceding replies suited, PP? Just in case they haven't, perhaps post some pretend data and what you hope the end result to be. I'm reasonably cluey but the use of "vice versa" is confusing me. Are you attempting to convert both things at once and are getting a circular reference warning (as column A depends on column B which might depend on column A which depends on...)?