Lua Need help with my "Mass Lifedrain" spell

[Demnish]

TFS 1.2

local combat = Combat()
combat:setParameter(COMBAT_PARAM_TYPE, COMBAT_LIFEDRAIN)
combat:setParameter(COMBAT_PARAM_EFFECT, CONST_ME_MAGIC_RED)
combat:setArea(createCombatArea(AREA_CIRCLE5X5))

local healing = Healing()
healing:setParameter(COMBAT_PARAM_TYPE, COMBAT_HEALING)
healing:setParameter(COMBAT_PARAM_EFFECT, CONST_ME_MAGIC_BLUE)
healing:setParameter(COMBAT_PARAM_DISPEL, CONDITION_PARALYZE)
combat:setParameter(COMBAT_PARAM_AGGRESSIVE, false)

function onGetFormulaValues(player, level, maglevel)
    local min = (maglevel * 10) + 25
    local max = (maglevel * 12.5) + 50
    if target == caster then
        return min, max --* targets affected
    end
    return -min, -max
end

combat:setCallback(CALLBACK_PARAM_LEVELMAGICVALUE, "onGetFormulaValues")
healing:setCallback(CALLBACK_PARAM_LEVELMAGICVALUE, "onGetFormulaValues")

function onCastSpell(creature, variant)
    return combat:execute(creature, variant)
    return healing:execute(caster, variant)
end

(I know "caster" doesn't exist and that "* targets affected" isn't a valid statement, but I put it there to give you an idea of how I want it to work)

What I want it to do is damage others and heal the user for the total damage done to all creatures affected by it.
I can see a bunch of problems with this spell, but I'm too much of a noob in LUA to fix it.