As data validation does not seem to be able to reference cells for numerical conditions (instead only being able to hardcode numbers); I have fallen back on conditional formatting. However, it does not seem to be possible to have more than any individual column affected by conditional formatting rule formulae
So while it is perfectly possible to do this:
Actually replicating this so that K3:K125 is compared with K1 does not seem to be possible. I would even settle for hardcoding all of the references like so:
However, this does not work.