Filter on a phrase in email Recipients' Names

[MacLingo]

I want to make a filter that identifies any Recipient of a multi-reciepient email who has "UU" in the associated email's address book name. So does "Recipient" refer to what's in my address book or what is actually in the corresponding received email address? The "UU" would not be part of the email address. And I would expect that to be the difference between "Recipient" and "From, To, Cc, Bcc". But it doesn't see to be the way it works for me.

Any suggestions most welcomed.
Mac