T-SQL (SS2K8) :: Convert Column In Query1 And Return Unmatched?

I have cpt codes in qry1 that need to be converted then match against qry2 and return the unmatched.

Example:

Cpt 88305 in qry1 can be either g4164 or g4165 in qry2
Cpt 88174 in qry1 can be either g3564 or g3565 or g3566 in qry2

select
Invoice_number
,cpt
From qry1
Select
Invoice_number
,cpt
From qry2

What is the easiest way to get the unmatched from qry1 against qry2 joining on invoice_number and converted cpt?