using Widget to fade Object

Hi guys,

i´m trying to fade an object in or out by the push of a button in game. I´ve made a 3D Widget (normal widget turned into a pawn and placed in the enviroment), it always looks at the player.

It works fine if i press it with the left mouse button (tested with “Print String”) but i don´t know how to toggle the visibility or fade my object in and out.
I´ve tried it with an actor blueprint for my mesh but i couldn´t get it to work. Any ideas?

Here´s a little overview of the project, the highlightet object should fade.

You can make a material, with a material parameter, and tweak that parameter when you press your button.