Adding value to existing field

[sj1601]

I have a sheet with existing data columns. Some data fields already have the data code in the adjacent cell but some don't. I have to find which data fields don't have values adjacent to them and place them there. For instance

Col A Col B
JO John
Smith
MA Mary

and so on.
I need to find all the Smiths (and other such data points) in the column and add the code "SM" in col A next to it.

I have another table which has all the Johns, Smiths and Marys, etc and their corresponding codes which we can use to fill in the blanks in this column.

Any ideas?

If my query is not clear please feel free to ask questions.

Thanks.

 

[SydneyGeek]

Let's assume your lookup table is in Sheet2!A1:B50

IF your lookup table is set like this: Code Name

Then the formula for A2 in the sheet witt the gaps will be
=INDEX(Sheet2!$A$1:$B$50,MATCH(B2,Sheet2!$A$1:$B$50,0))

If your lookup table is set like this: Name Code

This formula will do it:
=VLOOKUP(B2,Sheet2!$A$1:$B$50,2,FALSE)

Fill down

Denis