I have three columns set out as below:

A B C
L 123 Dec-07
M 456 Jan-08
S 789 May-07
E 123 Dec-07
L 456 Dec-07

Column C is formatted as text.

I need to sum items in B where A and C are a match. That is, if A = "L" and
C = "Dec-07" I need to get 579 from B. What formula should I be using? I have
played with LOOKUP, VLOOKUP and SUMPRODUCT but all to no avail.

AlexW