[AccessD] A Database Design Question

I have 4 tables (actually lots of instances of this setup, but for
simplicity let's deal with one only):

Customers -- obvious
CustomerDetails -- many Details for each Customer
Classifications -- a list of generic classifications
CustomerClassifications -- a table containing only the Classifications
of interest to a given Customer

The general idea is this. We populate Classifications with lots of
commonly-used items such as Admin, User, Manager, etc. We populate
CustomerClassifications using a combo and a NotInList event that allows
the addition of new Classifications that aren't already in the
Classifications table. When the user adds new CustomerDetails, we see
only the Classifications of interest to said Customer (i.e. draw them
from CustomerClassifications and get the text value for the combo from
Classifications).

Still with me? I hope so. Here's the question: should the table
CustomerDetails store the CustomerClassicationID or the
ClassificationID? 

TIA for opinions.

Arthur