Finally I found a way. It is probably not the most sexy one but it works perfectly !
After entering all the crazy commands that I could think of I tried to send twice in a raw the MSB LSB lines as this :
CC,ByteValue,MSB7bitValue,99,-2
CC,ByteValue,LSB7bitValue,98,-2
CC,ByteValue,MSB7bitValue,99,-2
CC,ByteValue,LSB7bitValue,98,-2
CC,Direct,Direct,6,-1
CC,ByteValue,LSB7bitValue,38,-1
And now everything is working properly, don’t know why…Maybe it gives the prophet VS time to go to the parameter to modulate…Anyway, no more value change on the previous parameter selected.
Now I can edit the VS and modulate it from my DAW. I m happy with it. The next step will be bi-directionnal communication but I am probably not enough strong in mathematics to put my head around all of those sysex stuff.
Maybe I’ll ask for help in some week for it 😉