I am not sure what exactly you want but this is the basic idea.

[![enter image description here][1]][1]


So we start by creating a random field. Then we re-scale one of the values, after  that we accumulate field and use it to set origin position and scale of the cubes.

The scale at index node group:

[![enter image description here][2]][2]

The frame produces a field full of 1 except at the selected index which is controllable. If you want to dynamically delete multiple cubes just repeat this node. 

[![enter image description here][3]][3]


  [1]: https://i.sstatic.net/fB5Wd.png
  [2]: https://i.sstatic.net/TAvTP.png
  [3]: https://i.sstatic.net/cwfiz.gif