sorry for my late answer, I was out of internet for a week ;-)
thanks a lot for your advice. In fact, I took my week off to think about what I really needed. I looked at the plugo tools where I found an echo midi plug in made with Max/MSP, I adapted it to my needs and integrated into my Drumbox M4L patch.
for the moment, I am not going to publish this new version of my "plug in", I rather prefer to play with it to see if it really suit to my needs :-)
I will keep you inform :-)