[geerdinho8]

pawn Код:

public OnPlayerRequestSpawn(playerid)
{
    new team1count, team2count;
    for(new i, m = GetMaxPlayers(); i < m; i++)
    {
        if (IsPlayerConnected(i))
        {
            if (gTeam[i] == TEAM_ONE) team1count++;
            else if (gTeam[i] == TEAM_TWO) team2count++;
        }
    }
    if (gTeam[playerid] == TEAM_ONE)
    {
        if (team1count > (team2count+1)){
        SendClientMessage(playerid, COLOR_YELLOW, "This team is full, please choose the other one.");
            return 0;
        }

    }
    else if (gTeam[playerid] == TEAM_TWO)
    {
        if ((team1count+1) < team2count){
        SendClientMessage(playerid, COLOR_YELLOW, "This team is full, please choose the other one.");
            return 0;
        }
    }
    return 1;
}

Good Luck with it!
Change the gTeams.