Assuming your source data is structured as below in cols A to C, from row1 down

A a 3
A b 5
A c 1
B b 2
B c 4
B d 9
etc

Just do a manual one-time fill from above for col A, to fully populate it.
If you have a lot of these to do, see Debra's page at:
http://www.contextures.com/xlDataEntry02.html
for some techniques

Then assuming inputs made in E1: A, in F1: c
Place in G1, array-enter (press CTRL+SHIFT+ENTER):
=INDEX($C$1:$C$100,MATCH(1,($A$1:$A$100=E1)*($B$1: $B$100=F1),0))
would return the required multiple criteria lookup result from col C, viz: 1

Copy G1 down to return correspondingly for other input pairs in E2:F2,
E3:F3, etc
Adjust the ranges to suit
--
Max
Singapore
http://savefile.com/projects/236895
xdemechanik
---
"muster" wrote:
I have a table like the following and I need to look up the 3rd column
based on the first 2. Anybody has a simple solution? Thanks a lot!

A a 3
b 5
c 1
B b 2
c 4