Hi,
I don't know whether there are any people here who know Cubase/Nuendo, the question is not software specific, but it might have a particular kind of solution in those programs.

It is about sending a Program change, normally, on any given track, you send a program change, and, if you want to use a different instrument later in the song, you send another Pr. Ch. with another number.
However, I use a virtual instrument called MyOrgan, which works like a real pipe organ.
You have to use one certain MIDI channel for a manual, another channel for another manual, and a different one for the pedalboard.
Now, every single manual and the pedalboard all have a number of different stops (sounds), which all have their own PC number.
Unlike a normal MIDI track, where you use 1 instrument per channel, you combine those stops and use certain combinations.
This works in Cubase/Nuendo by setting the numbers of the stops you need in the List Editor.
But now, the question is, what if all of a sudden, you want to change your combination by switching off one of your stops and keeping all the others active?
In other words, how do you switch a PC number off?

This is the tricky one, as normally you only have to use a different number to start using a different instrument, but how do you do the one above.

Sorry, it might be explained in a sort of semi Chinese, but it is a bit of a tricky one to express.

Any help will be much appreciated.