Slightly better code... maybe
I made some changes, so now the code looks like this:
Private Sub Combo14_AfterUpdate()
Dim ininventory As Boolean
ininventory = IIf(IsNull(DCount("[Item]", "tbItems", "[Item] = " & Chr(34) & [Item] & Chr(34))), True, False)
Me![Locked] = ininventory
End Sub...