If the secondary terms are unique to each value, you an sort on the field for the secondary term instead of the first.
But if you have to combine the two terms to get a unique value, then you'll need to make some other changes.
One possibility would be to set up a field in the value table that uses an auto-enter calculation to combine the data from two fields such as:
Field1 & " " & Field2
You would set up a unique values validation option on this field.
Then you would redefine your value list to list this combined field as the second field. You'd hide the first field.
And sometimes it just doesn't really work to use a value list and then other methods for selecting the correct value can be used.
Works perfect, thanks!