is there any way to determine if a cell has a validation rule dependent on the value of another cell?

what I want is:
C1 is "Core Business", apply a validation rule to C2 that only lets you pick from a list.
C1 is "Secondment", leave C2 as a free text cell with no validation rules.

I've already set up the lists for C1 and C2, I'm comfortable with that and with straight validation rules but not combined with IFs.

also did you have a haircut? it looks nice.