I've used a similiar method with both my kids. If they refuse to clean up their room, I wait until they are gone and clean it myself. When I clean, I put a lot of their favorite things in garbage bags and put the bags in the garage. When they keep their rooms clean, they get to go fetch things out of the bags in the garage. It works for my kids and I get to actualize that anger that they won't just do what they are told.