Texnixe, I'm very sorry, I just eplained exaclty the same thing in French.
And finally, you were both right, I did a big newbie error, my two folders were empty...I'm surprise to fall into a trap like that, I think this wasn't really clear in the doc.
So, thank you both. Dsply, youre plugin is exactly what I was looking for. It is amazingly helpfull. Contrary to ShopKit, this one is simplest.
A last question : did you finally resolve your "taxe" problem ? Because for me it is not. Why do we just put the price with the taxe already (TTC = in french, with all taxes) instead of doing this into the form ?