[gnulk]

So i figured it out, here is the snippet using 3 events.

-- A player has requested to duel me
function Duelist:DUEL_REQUESTED(event, playerName)
    opponentName = playerName
    duelingOn = true
 end
 
 --I requested a duel to my target
 function Duelist:CHAT_MSG_SYSTEM(event, text)
    if string.find(text, _G.ERR_DUEL_REQUESTED ) then
        if (UnitExists("target")) then
            duelingOn = true
            opponentName = UnitName("target")
        end
    end
 end
 
  -- The duel finished or was canceled
  function Duelist:DUEL_FINISHED(event)
    opponentName = ""
    duelingOn = false
  end