One misstake....

if field CBi contains text "*Z*"
then check in all other rows (except in row CBi !!) where the name in column AH (all rows!!) is the same as the name in field AGi, then check if in at least one of the rows of those identical ones, if in column CA also one times at least the text "*Z*" is registered.

Should be;
if field CBi contains text "*Z*"
then check in all other rows (except in row CBi !!) where the name in column AH (all rows!!) is the same as the name in field AGi, then check that in none of the rows of those identical ones, in column CA the text "*K*" is allowed.