excel - Assigning two column association to third column -

i have following structure in excel 2010

col1  col2   col3 12    c.e    c.e 13    d.c.e  c.e 14    p.e    p.e 100   a.o.h  a.o.h               c.e              p.e              ...              ...  output:   col3           12           12           14           100           12           14           ...           ... 

that col1 , col2 logically linked means c.e has value 12 , d.c.e has value 13.what want assign association col3 ever there c.e no matter how many times replaced 12 , ever there p.e replaced 14. having hard times doing please guide me how it?

if swap first 2 columns, can use vlookup function value associated particular text, so:

col1   col2   col3   col4    c.e.   12     c.e d.c.e  13     c.e p.e    14     p.e a.o.h  100    a.o.h   col4 cell value = vlookup(col4cell, $col1$firstrow : $col2$lastrowwithdata, 2, 0) 

note cannot directly replace values in col3 because lead circular references - check value in cell , replace in same cell!