Combining Items Problem

[D3AD UPR1S1NG]

I've been trying to combine these items to create the drill except I keep getting an error saying Combination Does Not Work anyone know what's wrong with this script?

void OnStart()
{
AddCombineCallback("", "hand_drill_part01_1", "hand_drill_part03_1", "Combine1", false);
}

void Combine1(string &in asItemA, string &in asItemB)
{
PlayGuiSound("12_make_drill.ogg", 100.0);
GivePlayerSanity(50.0);
RemoveItem(asItemA);
RemoveItem(asItemB);
GiveItem("", "hand_drill", "FinishedDrill", "hand_drill.tga", 0);
}

and yes it is in Inventory.hps anyone got any ideas?