I don’t know if Cubase works with inc/dec 
However, if you’re up for a bit more work, we can work to fake relative message that Cubase likes using Midi-ox.
Get it from here http://www.midiox.com/
It’s a very powerful (and low latency) midi monitor and editor.
You will have to add triggers that replace C96 and C97 with a combination of C6 and C38 (NRPN data insert) with values 1 and 16383 and set Cubase to accept the parameter as relative.