Update Variable from Sequencer

Hello,
I create a blueprint to move a mesh along a spline :

I create a sequence where I change the value of the variable who place the Mesh along the spline :

All is ok, I put the code in construction script and Event Graph. The variable is expose to cinematic and in class settings, I run construction script in sequencer.

But when I play, nothing append !!
You can see that I put a Print string to see the value of my variable. The value is ok but the mesh is not moving along the spline.

Can you tell me why ?
Thanks a lot for your help
Julien D.