Define a new relationship or modify your existing one. (I can't tell which option is best from just the info in your post.)
Right now you probably have two fields, one from each table set as match fields in your relationship. You should see something like:
I don't know the name of the table and field on the left hand side so I've used generic labels for that.
In Maintable, add a calc field that returns the text "CME", I'll call it "CMEKey"
Now set up a relationship that matches your two tables like this:
IDfield = Q_Rec_ID
AND CMEKey ≠ CME_Q
Now use this new or modified relationship in your count function.
(To edit a relationship, double click its line in the relationship graph.)
Count ( Subject 1::Q_Rec_ID ) - ValueCount ( FilterValues ( List ( Subject 1::CME_Q ) ; "CME" ) )
Thank you, that seems to be the most simple way of doing this!
What a great idea! Thanks Comment, that taught me a new trick!