no-one has released a program to do that.
it could be possible if the DS was left on during the process, HOWEVER i have a feeling that Inserting an R4 into the DS causes the DS to power off.
someone feel free to correct me if im wrong though.
or maybe it could be done with the solid state nor flash memory...
edit: then again, maikelsteneker says rudolph has a rom dumping tool with it, so maybe it is possible after all.