@L_Casier , I took a look at your block . You had a very good start, almost everything working as you would like but you were being stopped by the same hinderance many of us have encountered - the absence of a direction property for the rotation action. If only Autodesk had provided one we could do a lot more things and they would be so much easier.
However, I checked out another block where the author put a position parameter (actually you can call it a Point Move Parameter Set from the block authoring palettes) and then included the point in the rotation set. This works almost perfectly once you remove the weight assembly from the Distance1 move action set and add the new point move parameter (and give it the weight assembly as its action set) to the Distance1 move action and then chain Angle1 to Position1. The only thing left is to add Position1 to the flip set and it works. Unfortunately when any flip property is used on any chained parameters they tend to end up with errors in the X direction - for some unknown reason they end up doubling the X value of the objects involved in the chain when a flip action gets actuated. I have seen this enough times to consider it a flaw in Autodesk's dynamic block framework, but my only solution for my own needs with an inclined conveyor was to build two blocks, a left and a right.
I've attached a copy of your block with the changes described above and in this copy I deleted the flip parameter and changed the block to allow using differing x and y factors so you could mirror with the Mirror command and not need the flip parameter. It is about as close to a solution as I think you will find without using constraints (which happen to cause data corruption if more than a few are used along with dynamic properties in the same block.)
Hope this helps.
ADN CAD Developer/Operator