Moving platform with trigger radius

Game Modding | Call of Duty: Black Ops 3 | Scripting

ModmeBot:

Thread By: Pipi
I try to make a script for a platform made of two scriptmodel and a brushmodel.
It should go down when you stand on it and start playing a sound while it slowly goes down.
Then if you leave the platform the first sound stop and another short one play to let you know you failed while the platform goes back to its origin position, until you stay on it enough time to lock it down.
I know how to move things, but I don't know how to use a trigger radius (or if it is the best option) and how to stop a sound. Can someone help me with that? Even with tiny clues?

I think it is a good idea because it challenges you to stay at the same spot while dealing with the zombies; like in revelation or der eisendrache for turning on the low gravity.

note: sorry for my english