Are you trying to identify a row in the other table, or a column in the other table?
This response assumes row.
Performance wise have you thought of creating a mapping table. The initial setup will not be hard, but you will need some form of tool for adding additional records to the A_to_B table, for matches.
Table A
id, Field
Table A_to_B
Field, Code
Table B
Code, Description
If [blue]you have problems[/blue], I want [green]source code[/green] AND [green]error messages[/green], none of this [red]"there was an error crap"[/red]