We already have a job master for that. just put 0 under
set .Thirdclass,0;
the settings to disable third jobs.
it's inside your /npc/custom/
LINK to file in SVN
OnInit:
setarray .Rebirth[0],99,50; // Minimum base level, job level to rebirth OR change to third class
setarray .JobReq[0],10,40; // Minimum job level to turn into 1st class, 2nd class
set .ThirdClass,1; // Enable third classes? (1: yes / 0: no)
set .SNovice,45; // Minimum base level to turn into Super Novice
set .LastJob,1; // Enforce linear class changes? (1: yes / 0: no)
set .SkillPointCheck,1; // Force player to use up all skill points? (1: yes / 0: no)
set .Platinum,1; // Get platinum skills automatically? (1: yes / 0: no)
end;