Feel free to call me an idiot, but I need help!
If you have a Action Replay DUO, (the one for GBA and DS) and you are having trouble with the encounter codes for Ruby, try using Emerald... the codelist for emerald at gamefaqs have two sets of codes, and second set work on the DUO.
Apparently, the reason is that the DUO only lets you have one set of "ROM Patch Codes" on at once.