NPC Auto cast every 30 seconds

[lachadan1]

I have been trying get an NPC to auto cast a specific spell (spell ID 9412) every 30 seconds.

Scenario -> Teleporter NPC gets crowded by PCs that are afk, making it difficult for other PCs to target him. I want the NPC to cast a PBAE spell that knocks all PCs back 50 ft.

I have created the spell (9412) and have tested it using a script

sub EVENT_SAY {
if ($text=~/fire/i) {
$npc->CastSpell(9412, $userid);

This works and knocks back the PC hailing the NPC.

No, I can't seem to get this to fire every 30 seconds.

Any help?

Thanks.