Hi Sir
I confirm you are absolutely right in this schema with minor change for ending condition :)
SUM(R19:R27) should always = 1. (when R19, R21, R23, R25 and R27 are unlocked sum of all mentioned cells always equals 1 or in other words 100%)
a) B19, B21, B23, B25, B27, R19, R21, R23...