I need to count the number of existing customers retained season to season. So, if I have a range or orders written for a current season, I need to count all non-zero values in that range, so long as any previous season was also a non-zero. Obviously, this will compound season over season as customers that are new one season become existing/retained the next. I know broadly I need to set up a countifs with or logic, but for the life of me, I cannot get to a working formula. A simple countifs doesn't work beyond one previous season since it will preclude customers that may have written orders in one previous season but not the other.
Solved by V. U. in 21 mins