[SyntaxQ]

You have to set a timer.

pawn Код:

new sendername[MAX_PLAYER_NAME];
            GetPlayerName(playerid, sendername, sizeof(sendername));
            new namestring = strfind(sendername, "_", true);
            if(namestring == -1)
            {
                SendClientMessage(playerid, COLOR_YELLOW, "Your name must be in the Firstname_Lastname format - Please re-log with a name such as Amir_AB");
                SetTimerEx("KickPlayer", 500, false "i", playerid);
                return 1;
            } 
            forward KickPlayer (playerid)
            public KickPlayer (playerid)
            {
                  Kick(playerid);
            }