How do I set up complex qualifiers for Inventory managment?

I am attempting to put together an inventory managment & ordering system
(without resorting to switching to SAP) that allows me to use the following
criteria to define items:

Grade; Width; Finish

Each of these has multiple sub selections, but I want a number automaticly
assigned for each possible combination, and then under that each combination
needs to have a Unit number. (Think of: I want to know how many "Red Toyota
Camerys" I have in stock for an easy anology to what I am trying to do.) I
also need to be able to link it to a distributor ordering list (I work for a
manufacturer.)

I am attempting to do this with the Join function, however I have only
prolonged the project.