I have a table with two fields, the first a primary ID field, the second is memo. This table is used to store certain often used invoice item descriptions. It served my users fine, that is until now. You see, they are requesting that I incorporate a feature where they just have to select one Id and this ID in turn points to a few other ID, so that they do not have to select those items in each of their invoice line item. I am calling this Compound ID.

I am thinking of adding a few more fields to let my users define their own compound ID to those existing IDs. I know I can just add another table to do this. What I am worrying about is cyclic referencing. Example :-
ID Desc Points To
-------------------------------------------------------
A1 xxxxx -
A2 xxxxx -
C1 xxxxx A1, C2
C2 xxxxx A3, C1

How do I prevent this ? Should I use recursion ? If so how best to code ?

Thanks. I know you great guys should be able of offer some help.