If you are having trouble with ProfHalf, I would just go with the math option:
Code:
foreach pick in hero from BaseWep where "Helper.Proficient"
eachpick.field[dmmBonus].value += round(hero.childfound[ProfBonus].field[tProfBonus].value/2, 0 ,-1)
nexteach
Doing this from my head, but that should be correct...