Sequentially Enable Rigid Body Control

I would like to have a number of active RB objects set to animation so that they do not fall until their respective animation check-boxes are key-framed off. For a few objects, this can be done manually, one-by-one. My objective is to have perhaps hundreds of such objects with their respective key-frames corresponding to certain actions in the scene. For example, as an animated object gets close to one of the RBs, the RB's animation check-box gets keyed off and the object falls.

Can a driver be used but reacting based on distance from the RB instead of some rectangular coordinate.

Any ideas would be appreciated.

You can use Deactivation for this instead. Make the rigid body objects that you want to enable sequentially Active with Deactivation and Start deactivated enabled:

The rigid bodies will then start stationary, and only activate if another rigid body comes close to them. Even an animated rigid body can activate them:

using the same method i mentioned in this post: Novel Use of Drivers

You just have to change 1 line of the python code.

line 3 :

becomes

however you might want to change the LOC_Z to LOC_X or LOC_Y to use a different axis

object_name = "Cube"
import bpy
for obj in bpy.data.objects:
if  object_name+"_cell" in obj.name: