Instanced foliage actor

I’m wondering if there is a way of accessing to the properties (like changing the material) of some singles instances of the foliage.
what i want to achieve is if the player in a top down view enter a big forest (created with a volume spawner on the terrain), can hide the trees between the camera and the player using a raycast eider by changing the material or a parameter of the material on those trees.
is it possible?