I decided to add a timer controlled solenoid to my CO2 system yesterday. So I called up my local supplier and found he had a 120v three port solenoid for $20. After picking up the solenoid and some neat little check valves that screw right into my needle valves I headed to the BORG for a couple of small plumbing parts and I was ready to go. Here's a picture for those that are interested.
Note the very small brass check valve attached to the needle valve!