Yamaha DTXpress/DTXplorer/DTXtreme

Hi,
  I'm in need of some serious help.  
I have a Dtxpress 1 and I'm trying to record into Cubase SX however, 
what I'm trying to do is play the DTXpress via midi into Cubase 
(which  works fine) but then what I need to do is playback the midi 
file which I create and midi out it to the Dtxpress so that it can 
then record the Dtxpress drum sounds on individual tracks in Cubase so 
that I can mix them down individually.  At the moment all I'm getting 
is pianos and bass sounds from the Dtxpress but no drum sound.
Can some one please help???

Thanks in advance

Fusion