How to do Chain damage

Soo uhh hi!

Im working on a childhood mod I wanted to do for so long (5 years) and im stuck. Idk how to do chain damage like you kill a mob and all the mobs in a 7 block radius with less than 50 hp get 45 damage

I did something like this

If Max health of event/target entity < 50

do If current health of event/ target entity = 0

do if does entity exist at x 7 + -7 y 7 + -7 z 7 + -7 in square cube size of 7 of type mob entity

do deal 45 damage to event/target entity type GENERIC

Please help

-ItsDaAltron :D

why does this sound like my math homework