Value Mapping - I don't want an error returned if not found

For each record I'm bringing in through AIF, I'm running it through a Value Mapping that will convert a Plant Code to a different value. The problem is that this, right now it is only applicable for 1 certain Plant so I only have 1 entry in my Value Mapping.

For instance, if the plant code is AAAA, I want to overwrite that with BBBB. So, I have created that entry in my Value Mapping table.

The problem is that when my message has a plant code of CCCC, the message errors out because CCCC doesn't exist in the Value Mapping table.

I need the message to retain CCCC since no mapping value was found and continue processing.

What would be the best way to accomplish that?

Thanks,

Robert.