Lua Poison Arrow (onUseWeapon)

[felzan]

I'm trying to do a poison arrow that deals damage based on target health.
I can get the target health but only when i hit (with the arrow)

the question: How to get target health on each condition event?

local combatArrow = Combat()
combatArrow:setParameter(COMBAT_PARAM_DISTANCEEFFECT, CONST_ANI_POISONARROW)
combatArrow:setParameter(COMBAT_PARAM_TYPE, COMBAT_POISONDAMAGE)
combatArrow:setFormula(COMBAT_FORMULA_SKILL, 1, 0, 1, 0)

  local function onUseWeaponPoison(parameters)
      local target = parameters.cid:getTarget()
     
      if target == nil then
          return true
      else
      local conditionPoison = Condition(CONDITION_POISON)
      conditionPoison:setParameter(CONDITION_PARAM_DELAYED, true)

     
      for i = 10, 1,-1 do
        local hp = getCreatureHealth(target)
        local hpp = .001
        conditionPoison:addDamage(1, 1000, -hp*hpp*i)
      end

      combatArrow:setCondition(conditionPoison)
  end
  end

function onUseWeapon(player, var)
  local cid = player:getId()
  parameters = {cid = player, var = var}
  combatArrow:execute(player, var)
  addEvent(onUseWeaponPoison, 1000, parameters)
  return true
end