Need a function to apply a factor to certain values (col2) in a large table
if val in same row, col3 is one of 13 codes - a list in col6. For
illustration (caps letters denote excel column labels):

A B C D E F G H I J K L M

23 a b
14 c g
42 d e
31 b
64 f
23 g
99 g

so for this example, the function would be inserted in a new column, say L.
It looks for instances of b,e and g in col B and if found returns the
corresponding value in Col A* a factor.

Suggestions appreciated. Or(Exact) doesn't work.
Thanks