Not really sure that this is what you are looking for:
I've implemented a function to return the value in column C if a match
is found in columns A & B.
Note that only the first match is returned - based on your post I assume
that the matches in A & B are always unique.
Call the Function with
=Factor("String to find in first Column", "String to find in 2nd
Column", Range to search in First Column)
If there is no match zero is returned.
Function Factor(A As String, B As String, C As Range) As Variant
Dim D As Range
For Each D In C
If D.Value = A Then
If D.Offset(0, 1) = B Then
Factor = D.Offset(0, 2)
Factor = 0