All my retail cds are marked as such in the cd/dvd database by having a custom field filled with Retail. When I rip a cd, that tag is set on the ripped files too.
[archive]=retail ~sort=[import date]-d lists all files that have been ripped from retail cds with the most recent rips at the top.
MC's [date imported] field includes the time imported as well as the date, and I find that often queers the lists, so I made an [import date] field to sort by using FormatDate([Date Imported,0], yyyy//MM//dd) and get much better results from that.
If you choose a similar route, I'd still base your exclusion on the [date imported] field....
[archive]=retail ~sort=[import date]-d [date imported]=<20d