How to detect for collisions and run scripts on other objects during specific animation frames?

I’ve set up a walking animation so that it plays a giant mech footstep sound effect when it hits the ground in that animation event. I also have a box collider around the feet set as a trigger so it can crush enemies and cars while walking. Only, I can’t figure out how to make that trigger -only- during the frames where it looks like the animation is stepping down, and it instead does it all the time.

Can you activate/deactivate the collider depending on animation time?