How do i change the opacity of a material inside an emitter via blueprints?

I have tried already to Create Dynamic Material Instance and then from its return value Set Scalar Parameter Value, but it doesn’t seem to work. I think it does change th

e parameter value as when i geth the scalar parameter it does return the correct value, but it might be that the emitter already spawned the particles with the material. What i am trying to do is to have the player that spawns this effect see it with a lower opacity than other players.