Callback when 2 agents are in close proximity?

Hey, I have a number of agents using the RVO Simulator. I want to detect when 2 of these agents come into close contact and then call a function to cause damage to one of them.
Is there some sort of callback function that fires when agents come within the radius of another? This is very performance sensitive so I would like to utilise the same calculation from the RVO controller if possible.

Thanks for any help.