Oh, thanks to you I found the “set update animation in editor” node 
Actually I already get the target as a variable to get its location. The animation is updated durig Event Tick (I can’t set the target directly as a variable in the animation blueprint).
Another question though : the final rig is made by 2 two-bone IK (bone003 to Bone005, Bone005 to Bone007) and one look at (Bone006). Updating the animation only takes care of the first target and updates the first ik, not the second one. Any idea ?
EDIT : alright it is due to another rotation of the root bone that makes the whole thing bad. Thanks a lot !