Not sure if it's meant for SS or HG; I got it from the "Pokemon HG/SS: Completely Random!" topic and it seems to be working for other people there. I'm not using a premade cheat database; all I have in there is the random wild pokemon cheat (which isn't associated with buttons at all), the "990 of every ball" cheat (which works with UP+SELECT properly), and a cheat for money in Infinite Space (which is also not working).
EDIT! I tried again, this time ganking the TEMP USRCHEAT.DAT and editing it, and got more or less the same results. The code that allows you to view IVs/EVs with R/L works, the code that gives you all pokeballs with Up+Select works, the meet-random-wild-pokemon code doesn't. I'm going to go ahead and guess it's a problem with that particular code, and just keep asking in that thread. Thanks for the help, guys.