You need to store the location in variables, mark it as "selected" or something with a boolean, then in the next sub-event's conditions pick all objects of the same type*, then exclude the selected object and after that add a pick closest to X,Y condition.
Please see capx as an example:
https://www.dropbox.com/s/z1df71tscepzr ... .capx?dl=1
*remember every condition picks only out of the objects exluded by the conditions before/above it, you need to make sure you are selecting out of all objects again hence why you need pick all which resets it to all, then you narrow it down to all but the selected one.