Definitely had fun working out how to use the error message tool! Video solution here: https://www.youtube.com/watch?v=VcYazkiYZD4&list=PL18SpOXDj-KMUD4YwWC5vZaUsIa7drxNZ&index=42
What a fantastic problem to apps and interface configurations. Workflow is pretty direct for solving, but parameterizing was a fun brain game. Bonus Error checks added albeit maybe not the most elegant formulas.