[Kingunit]

You need to create something new.
Like

pawn Код:

if(Player[playerid][Event] == 1)
    {
        // Here you'r actions.
        Player[playerid][Event] = 1;
    }

Then you can check at every teleport:

pawn Код:

if(Player[playerid][Event] > 0) return SendClientMessage(playerid, 0xFF6347AA ,"You are already in a event, type /leavedm to leave.");