In fences, INIT field:cutit = this addaction ["Cut fence","cut.sqs"]
In cut.sqs:
Fence setpos [getpos fence select 0, getpos fence select 1, (getpos fence select 2) +10000]
ruinedfence setpos [getpos ruinedfence select 0, getpos ruinedfence select 1, (getpos ruinedfence select 2) +0]
name the fence fence...
place a destroyed fence st the same location, but put this in the Init field:
this setpos [getpos this select 0, getpos this select 1, (getpos this select 2) +10000]
The ruined fence will start at 10000 altitude, and it will stay there until someone approach the fence, and cut it, even AIs can do this if you order them to...
this will only apply to a single fence section...unless you make a scrript and variables for every fence section...