Stop Condition Evaluating Displacement at a Specific Point?

Hello,

In a simulation I'm running, I'm measuring the time it takes for a given domain to relax after an initial displacement is induced. The relaxation times for my models vary greatly so my current approach is to run the simulation for a long period of time (longer than I expect the relaxation time to be), then manually find the relaxation time for when the displacement at a point returns to 0 (or nearly 0).

What I would like to do is have COMSOL automatically stop solving a model once the displacement at a given point becomes 0 (or nearly 0), using stop conditions. My issue is that I don't know how to define a variable that the stop condition can recognize. I've tried things like:

Stop condition = 5e-12 - v(0, 25 [mm])
(my model is 2D with a domain of 4cmx5cm, trying to probe the vertical displacement at 0, 25 [mm])

Stop condition = 5e-12 - pbb1
(pbb1 is point probe at the location I'm interested in)

But both throw errors when I try to solve them. What can I do to get a global variable to be set to the solved displacement of a point at the given time?

Thanks so much for any help you can offer, it is greatly appreciated!