Here's another option: Collect the fence object ids you need into an array. Then set up a script that loops through the array and tests the distance of the player to the object. When player is close enough, add the action to the player, and register the near object id in a global variable (so the destroy action knows which object to destroy). When player moves away (or fence section destroyed), remove action from player, and remove object id from global variable. Be sure to sleep in the loop so it doesn't use up too much cpu.
If you want many different possible fence breakpoints, this approach may be cleaner, as your Destroy script is simple: It destroys the object whose object ID is in the global variable.
If you have to place hidden objects or game logics for each fence break point, your destroy script becomes more complex, as it must be able to know which object id corresponds to which placed object/logic.