If I have 3 groups: each holding a distinct # of combinations:

Group A(1 to 3) B(1 to 2) and C(1 to 3)

How can I create a unique "sequential" ID for each unique

possibility? (There are 18 possibilities in this example,

so I would need an ID from 1 to 18 for each one)

so from 1 to total # of combinations as the ID.

Also note if A= 1, B=1, C=2 you cannot simply multiply since

if A=2, B=1, C=1 it produces the same ID.

Your help is appreciated.