I have a sheet of data which runs horizontally containing 12 months of data.
I need a formula which will lookup criteria horizontally as well as
vertically and return the summed value of all occurences. So I would like it
to sum all instances of FR and abc when row 1 equals Nov-05 and row 2 equals
OOH.

A B C D
1 Nov-05 Nov-05
2 REP CUST OOH VALUE
3 FR abc 100 300
4 FR abc 200 100
5 JPZ def 300 200
6 JPZ def 100 300
7 JPZ ghi 200 100
8 JPZ ghi 300 200

Thank you in advance,

Esther