Second promotion script

[stinkyschool]

I have a script for a promotion and i added another promotion and it work perfect but i noticed that you could first promotion again and it would give you the second promotion... I need someone to help me put in a restriction and something that will say you already have this promotion. Here is the script i have...

local keywordHandler = KeywordHandler:new()
local npcHandler = NpcHandler:new(keywordHandler)
NpcSystem.parseParameters(npcHandler)

function onCreatureAppear(cid) npcHandlernCreatureAppear(cid) end
function onCreatureDisappear(cid) npcHandlernCreatureDisappear(cid) end
function onCreatureSay(cid, type, msg) npcHandlernCreatureSay(cid, type, msg) end
function onThink() npcHandlernThink() end

local node1 = keywordHandler:addKeyword({'first promot'}, StdModule.say, {npcHandler = npcHandler, onlyFocus = true, text = 'I can promote you for 20000 gold coins. Do you want me to promote you?'})
node1:addChildKeyword({'yes'}, StdModule.promotePlayer, {npcHandler = npcHandler, cost = 20000, level = 20, text = 'Congratulations! You are now promoted.'})
node1:addChildKeyword({'no'}, StdModule.say, {npcHandler = npcHandler, onlyFocus = true, text = 'Alright then. Come back when you are ready.', reset = true})

local node2 = keywordHandler:addKeyword({'second promot'}, StdModule.say, {npcHandler = npcHandler, onlyFocus = true, text = 'I can promote you for 50000 gold coins. Do you want me to promote you?'})
node2:addChildKeyword({'yes'}, StdModule.promotePlayer, {npcHandler = npcHandler, cost = 50000, level = 50, text = 'Congratulations! You are now promoted.'})
node2:addChildKeyword({'no'}, StdModule.say, {npcHandler = npcHandler, onlyFocus = true, text = 'Alright then. Come back when you are ready.', reset = true})

npcHandler:addModule(FocusModule:new())