Lifesteal Attack

[Epicxz]

So i am trying to figure out how to make a lifestealing attack, usinga brutal attack like spell so i have

local combat = createCombatObject()
setCombatParam(combat, COMBAT_PARAM_TYPE, COMBAT_PHYSICALDAMAGE)
setCombatParam(combat, COMBAT_PARAM_BLOCKARMOR, 1)
setCombatParam(combat, COMBAT_PARAM_EFFECT, CONST_ME_HITAREA)
setCombatParam(combat, COMBAT_PARAM_DISTANCEEFFECT, CONST_ANI_WEAPONTYPE)
setCombatParam(combat, COMBAT_PARAM_USECHARGES, 1)

function onGetFormulaValues(cid, skill, attack, factor)
local skillTotal, levelTotal = skill * attack, getPlayerLevel(cid) / 5
return -(((skillTotal * 0.02) + 4) + (levelTotal)), -(((skillTotal * 0.04) + 9) + (levelTotal))
end

setCombatCallback(combat, CALLBACK_PARAM_SKILLVALUE, "onGetFormulaValues")

function onCastSpell(cid, var)
return doCombat(cid, combat, var)
end


so this is for brutal strike, how would i set it to make X% of damage done return as health to the player?