update your topic title, to request.
Later edit >.>
Hope your not expecting a script xD, heres how you should do it:
I. Things you'll need: 3 fields - 1 int[3] array containing the spawn point (or just do it dirty), 2 int field witch the last npc id will be incremented, 3 an array with npc ids
II. When you will you use spawn method make sure u increment the npc id to the "last used npc field".
III. To restart the procedure, check if the last npc id of the npcId array is also the last incremented npcid, set the "last used npc field" to the first entry of the npcid array.
IV. Create a runnable task for the spawning procedure, also you could set the runnable's constructor handle the next npc parsing.
Hope it helps, cheers.