Syncing Midi Device (writing beats in Cubase)

Hi

I have my Korg Volca synced to cubase via a midi cable. I can record loops I have written on the Volca at and given tempo (set via cubase) onto an audio track.

However, if I try and write in a beat manually using the drum editor I only get one sample played back no matter where I hit on the piano roll. I have to change the channel on the MIDI track to select a different sample. This ultimately means I can only write in one part for each midi track!

Is there any way round this?