Expected Identifier Error

[bkrstirregular]

I think I'll be making a lot of these tonight..I'm getting so frustrated with coding that I want to pull my hair out ;_;

//AddUseItemCallback
AddUseItemCallback("", "Key_1", "firstdoor1", "UsedKeyOnDoor", true);
{
void UsedKeyOnDoor(string &in asItem, string &in asEntity){
SetSwingDoorLocked("firstdoor1", false, true);
PlaySoundAtEntity("", "unlock_door", "firstdoor1", 0, false);
RemoveItem("Key_1");
}


Can someone tell me what I've done wrong here?