volume of midi track and the kontakt instrument are controled in the same time by the X-touch fader


i have a problem with a controler (behringer x-touch) and cubase 5 with Kontakt. I use Kontakt by the Vsti section, and i put a midi track with it. my x-touch is in Mackie control protocol. the problem is when i up and down the fader button, it move the volume of my track but also the volume of the instrument in kontakt. how ca i dissociate bleep? because this volumes are note the same and dont have the same fonction so it’s a problem.
i dont have the problem when i us an “instrument” track instead of a midi track, but the problem of the “instrument” track is that i have to use a new kontakt for each track…so it’s not a good option.
I dont know if the problem is a setting in the X-touch or in cubase or in kontakt?

Thanks a lot,