Hacking Usrcheat.dat?

[NekoKat]

So, here's the thing. I have a urscheat.dat, updated and all. Under normal circumstances, it works with Mega Man Battle Network 5 DS, but I replaced the soundfile from MMNBN5DTDS with the japanese version, RMEXE5DSTL, under the grounds the american voices just... well, annoy me to hell and back.

But the usrcheat.dat file won't work! Why!? Only the sound file was changed in the ROM (using DS Lazy)...

Thanks