in Merchant, you set the NPC as normal..
In Chimera's example, the NPC is at Map 0 X9 Y14
Now in ANY NPC's script, do a link that runs the #ACT as Chimera put it
#ACT
MoveNPC "0,9,14,John_(accessories)" 5 63 196
So, it will move the NPC with the name John_(accessories) from Map 0 X9 Y 14 to...