Assign material instance to multiple mesh from a Blueprint

Hello, I have a little problem and i can’t find solution on the internet :

So I have several object inside an Actor Blueprint

And when I press play I want to change the Transparency parameters to 0 for all of them (inside a widget blueprint), my current technique is to call them one by one and change the value

but I wonder if there is an automatic way to do that ?

I’m french and beginner so don’t be to hard with me :wink:
Thank you !

Inside the actor:

Oooh yeah ! Mega huge thanks !!! for me you are like Pamela Anderson from Baywatch