OK, when a user logs in with security assist, the users ID is stored in a session variable.
This user id can be used to create the relationship between the selected products, then used to filter the recordset to display them
The userlevel authentication tutorial on the security assist support page talks more about the session variables that are created on login, how to add them and use them in creating page access rules.
the sessions can also be used when creating recordsets, see the profile page for an example, and in the insert record and update record behaviors.