Ok, I experimented some more but with little success again. I, however, finalized the cube itself, so maybe it is easier to grasp what i wanna do.
All sides of the cube are 1x1 studs held by a 10x10 net. I want all sides do move more or less randomly to make it look like they're pulsating. My initial idea was to attach something that moves back and forth to the center of the netted surface from the inside. Slowly I am getting the feeling this is not the best approach.
Also, in case you're wondering. One side is 10 x 10 studs x 4 pieces = 400 pieces. Times 6 for each side = 2400 1x1 plates/tiles. Took some time to assemble it. XD