How would I constantly detect if two players are within a certain magnitude?

Hello! So, I wanted to make a little game where players have to try to get within a magnitude of 8 in between each other with lots of obstacles in their path. I wanted to know, how would I set up a listener to constantly check for any change in their magnitude? An idea I had was to set up a separate listener for each player that runs on a player.Position.Changed event but I felt like it might cause too many glitches as the player’s position changes a lot of times and I felt that if I ran an event each time that happened, it would damage performance. Does anyone know any better solutions?
Thanks!

You could use renderstep API. I’m not that familiar with it, but I know it exists.