Returning /Naming variable name of object that comes close to another??

hi
I’m trying to figure out the correct puzzles to use and how to use them for this task.
I have 6 objects who’s names are listed in a list, and are in a group.
they all at some point pass by an empty called “sensor”
id’ like to update a variable with the name of whichever one is currently passing by it. (nothing needs to physically collide in this scene)

I an trying with “distance between” puzzle …and also i tried with the “detect collision” and “collision info”.. as they pass through each other..
no dice.

how do i get the name of whatever object is “at” the null?