As meko is correct, this script command wouldnt be more appropiate?
areamobuseskill("<map name>", <x>, <y>, <range>, <mob id>, <skill id>, <skill level>, <cast time>, <cancelable>, <emotion>, <target type>)
*areamobuseskill("<map name>", <x>, <y>, <range>, <mob id>, "<skill name>", <skill level>, <cast time>, <cancelable>, <emotion>, <target type>)
This command will make all monsters of the specified mob ID in the
specified area use the specified skill. Map name, x, and y define the
center of the area, which extending <range> cells in each direction (ex: a
range of 3 would create a 7x7 square). The skill can be specified by skill
ID or name. <cast time> is in milliseconds (1000 = 1 second), and the rest
should be self-explanatory.
<target type> can be:
0 = self
1 = the mob's current target
2 = the mob's master
3 = random target
Example:
// spawn 1 Shining Plant in the 5x5 area centered on (155,188)
areamonster("prontera", 153, 186, 157, 190, "Shining Plant", SHINING_PLANT, 1);
// make the plant cast level 10 Cold Bolt on a random target
areamobuseskill("prontera", 155, 188, 2, SHINING_PLANT, MG_COLDBOLT, 10, 3000, 1, e_gg, 3)