Yamaha DTXpress/DTXplorer/DTXtreme

I would like to use the DTx3 to play back midi files as backing 
tracks.  I know that I can do this through a pc, but is there any way 
of tranfering a midi file dirctly into a user song area.  I have 
tried playing a midi on the pc and recording to the DTx, but run out 
of memory before the end of the song.

Any help apreciated.