I would not do it that way.. way too easy for it to leak oxygen back in and revive the mouse.

Go get a plastic container with a tight fitting lid (I used a big tub that had cheese balls in it originally) and drill a hole in the side of it near the bottom. Put the Co2 remote (cord) in there and seal it with something (I used hot glue.. caulk would probably work too)

Next drill a small hole in the lid of the container and run aquarium airline (the flexible clear plastic tubing used for bubblers) through the hole. Seal it like you sealed the remote line, and run the other end of the airline into a bucket of water. This is your exhaust line that keeps oxygen from getting back into the container.

Hope that made sense.