OK, I can't get it working but I'm willing to accept the possibility that I'm just stupid.
I'm using v1.18 of the r4 firmware.
I'm using the rom named: ind-nngj.nds
I set up the cheat using the Chead Code Editor off the R4 site,
the game ID is YFQJ bcac3b62
and the cheat code, that I named...