I use Excel a lot, and run a team that use it more. One of biggest tips I give is to not write complex formulae if you can help it. Split it into more cells, so it goes step by step. It looks less cool, but when you have to edit it in 6 months you will thank me.

It is not always possible, of course. But it normally is. For the edge cases a helper like this must be nice. Maybe some fields have lots of edge cases, mine has few.

Excel is often an exercise in the equivalent of writing Perl one-liners, except without the charm of wondering to yourself if you could win an IOCC contest.