Lua Exploding Health Rune - how to make it for KNIGHTS only!

[Snooczek]

local exhaust = createConditionObject(CONDITION_EXHAUST)
setConditionParam(exhaust, CONDITION_PARAM_TICKS, (getConfigInfo('timeBetweenExActions') - 100))

function onUse(cid, item, fromPosition, itemEx, toPosition, blah, var)
	local level = getPlayerLevel(cid)
	local mlevel = getPlayerMagLevel(cid)
	local health_minimum = (level * 5) + (mlevel * 5) - 50
	local health_maximum = (level * 5.9) + (mlevel * 5)
	local health_add = math.random(health_minimum, health_maximum)
	
	doCreatureAddHealth(cid, health_add)
	doSendMagicEffect(getThingPos(itemEx.uid), CONST_ME_HEARTS)
	doCreatureSay(itemEx.uid, "Aaaah...", TALKTYPE_ORANGE_1)
	return TRUE
	end

Guys, please! Tell me how to make it for KNIGHTS of level 200 and higher?
I tried many times to fix it but im not a good scripter - just a newbie. And i think that i'll find some help in here