Content of ID on the Last record of a DB

Hi
I've a DB with some fields ... one of then is an auto-increment ID.
i've to create an adherent number.
I need the month ( 2 digits ), Year ( 2 digits ), dept number ( 2
digits) and finaly the ID to conctene with the other parts.
So I need the ID of the last record of my DB ( to calculate the ID of
this current record ) .
So , is it possible to know the ID of the current record or is it
better to have the content of ID field of the last of this DB. ?
And how to do this
Many thanks