AE – make 2D layers a 3D stack

position+[0,0,(index-2)*thisComp.layer(“3D Control”).effect(“3D Control”)(“Slider”)]

 

with the null being named 3D Control

 

taken from :

 

http://ae.tutsplus.com/tutorials/motion-graphics/how-to-create-a-seamless-infinite-white-backdrop/