Find missing values - based on looking up a list, comparing against index values

Hi all,

I've got a particularly curly problem that I've been unable to solve so far. Was hoping someone here might be able to shed a bit more light.

I have 2 lists that I need to compare - with a twist.
List A contains a name in the first column and a code in the second column. The name may be repeated multiple times, and each time it is repeated it may be assigned a different code.
List B contains a list of all the possible codes that may be used in list A column 2.

What I'd like to be able to do is discover which codes that exist in List B have not been used for each name in List A.
Essentially List B could be treated like a VLookup table (in my mind) - I'm just not sure how to write this up.

Let me illustrate for clarities sake - notice how in the REUSLTS section only the missing codes are displayed

MissingCodesV2.jpg

Thhank you very much for all your help - and please don't be afraid to let me know if I've missed out on something.