[SCRIPT] Can't get area script to work!

[Amphen]

Hellow I'm a new scripter and I really could need some help solving this problem.
In my level editor I've made an area called "ScriptArea_1". When the player enters the area I want a barrel and a sound to appear, but whatever I do it wouldn't work!
Here's my script:
void onstart()
{
AddEntityCollideCallback("player", "ScriptArea_1", "appear", true, 1);
}
void appear(string &in asParent, string &in asChild, int alState)
{
PlaySoundAtEntity("", "react_scare", "player", 0, false);
SetEntityActive("barrel02", true);
}
If anyone could help me I would be very appreciated!