You could also use Variabels:
void OnStart()
{
SetEntityCallbackFunc("ItemYouWantToPickUp", "PickupItem");
AddEntityCollideCallback("Player", "CollideArea", "CollideArea", false, 0);
SetLocalVarInt("RandomName", 0);
}
void PickupItem(string &in asEntity, string &in OnPickup)
{
SetLocalVarInt("RandomName", 1);
}
void CollideArea(string &in asEntity, string &in asChild, int alState)
{
if(GetLocalVarInt("RandomName")==1)
{
PlaySoundAtEntity(blablabla);
}
else if(GetLocalVarInt("RandomName")==0)
{ //Do nothing
}
}
What it basicly does is that when you pick up the item, it adds a number to the variable. When you walk into the area, you can now hear the sound.