Help with armor enchantment attribute

Hi guys, me need help with enchantment, i create enchantment-extra health, after im load plugin attributes and create procedure:

 If armor in armor slot have enchantment extra health

 do set value base of attribute max health  of event/target enemy to max health of event/target enemy + 4 (2 hearts)

But this procedure adds infinitely +4 to my health(20-24-28-32-36...) how i can stop it when it do one time( to set just +4 one time not infinity)?