To the OP Maxine........
Could it be done? Probably yes......
Has it be done? Probably yes......
Is it a good idea? Probably no.
If you really want chickens and being gone for a week or so at a time is your situation, the best and really only option is to make the entire setup Fort Knox. A predator proof coop that nothing.....absolutely nothing can get in....day or night......and if you have a run, same thing. Just know that having a run makes it so much more difficult to make it predator proof. Best option for that is to have a house/coop that is large enough, and fitted out well enough they an stay in for that period of time.
I have left the birds in my Woods coop for as long as 3 or 4 days at a stretch, unattended, and had no consequences. They were all still alive when I got back. House is adequate for up to 24 birds and right now there are only 7 in it. Not something I would ever do routinely, but it has happened.
Big issues are food and water. Things that seem fool proof may not be. If you provide an adequate amount of water in a bucket with nipples so the water stays clean.......what happens if a nipple pops out and all the water drains out? So perhaps at least 2 and maybe 3 water buckets? What about climate? Are you in an area where the water can freeze solid? What happens if the power goes out?
If a predator does break in, power goes out, water goes dry, whatever......worst case scenario is they will all be dead when you get back. If that is something you are prepared to accept, then let your conscious be your guide?