Hello Ronaldo
Rather than using sets, built for other purposes like report systems in the SAP ERP, I'd suggest to use table TVARV. This was designed to provide variants for ABAP reports, but it can be easily used to store ranges and fixed values for programs.
Values can be set in transaction STVARV and a sample code to retrieve values can be found here:
http://www.abapzombie.com/guias/2011/01/20/codigos-pequenos-e-uteis-parte-1-tvarv/
Regards
Luis Becker