Writing the code won't be difficult! The strings are quite simple for AN200, kinda.
If you look at page 133 of manual, under <2-2> you'll see:
MIDI Parameter Change table ( SYSTEM )
and then it says:
Step Seq Loop Type forward(0),backward(1),alternateA(2),alternateB(3)
Which has to mean the sequencer can be played in those modes?!! Surely? It doesn't make sense for it to be for anything else on the synthesizer.
The code I've tried to program is: F0 43 10 6D 0 0 9 XX F7 (XX = data from knob/slider)
Let me know what you think?