Combining script isn´t working. Please help

[Melvin]

void OnStart()
{
AddCombineCallback("", "stick", "rock", "CombineFunc", true);
}

void CombineFunc(string &in asItemA, string &in asItemB)
{
PlayGuiSound("15_make_hammer", 1.0f);
RemoveItem("stick");
RemoveItem("rock");
GiveItem("stone_hammer", "Puzzle", "stone_hammer", "stone_hammer.tga", 0);
}


void OnLeave()
{
}


This should work, if not, try looking into your leveleditor for typos or capital letters.
what exactly isn't working? Can you be a little more specific?