I've just gotten a large number of immigrants, most of whom I don't want, and I would like to get rid of them. I have a small room set up to flood with water, but short of giving those dwarfs I want to kill a bedroom in there I'm not sure how to get them to stay in there. So, basically, what is a good method to order a specific group of dwarfs to stay in this room so I can drown them?
Game version is 40d.