How to make an object move to the direction in which the user faces using vr gaze interaction?

Here you can see the sphere and cube were the reticle is pointed. I did this watching nurface games tutorial about vr gaze interaction (12.00)minutes video.now my doubt is "when the user gazes at the cube it should come forward.ie It should go to the direction that the user gazes at.then if the user gazes at sphere the cube should go backwards and sphere should come forward.can anyone please help me with this?