Electronic CO2 Solenoid Valve

I want to control this on a timer. I have a Hydro X so a timer is no problem for the fans, but I have to shut the C)2 off before I can put exhaust fans on.
What kind of regulator will work in this situation? Are there reasonable priced digital regulators that can work off and on off switch?

For aquariums there are solenoids to be put behind the regulator. You shouldn't have a problem to get a used one.