Thanks for that pezzott1
Understand the logic now just need to put that in place.
What I have in place is the door, an Arrow and a cube.
The arrow and the cube got the same position in the Door_BP
The arrow though is parented to the door, so move with it.
My goal was to get the position of that arrow and the one from the cube (That is picked up by the controller) and just doing a difference float in between them in X axis and add that difference to the X axis of the door.
Surely it is wrong as it is not working 
I will try to figure out what you explain and give it a go.
Thanks again for your help
Take care
Cheers,
Matthieu