For classes used in forms, you can scan the .pjx for 'scx'$name, open each .scx as a file and do a select SQL for not empty(classloc), something like this:

USE myPrj
SCAN FOR 'SCX'$UPPER(name)
  lcFormFile = JUSTFNAME(myPrj.name)
  use (lcFormFile) in 0 alias FormFile
  SELECT PADR(JUSTFNAME(classloc),50,' ') AS clib, ;
         PADR(class,30,' ') AS cclass ;
    FROM FormFile ORDER BY 1,2 ;
    WHERE NOT EMPTY(classloc) ;
    INTO CURSOR QClasses
  * print or store the info
  USE IN FormFile
ENDSCAN