I've never done it myself but I've considered it. If you do, you will need to make sure that you can both contain the atmosphere within the tent and remove heat buildup. That is probably the biggest stumbling block for using co2 in small grows versus the bigger, self-contained grows where the internal atmosphere is cooled with AC.
You could do it with an alternating ventilation/co2 injection, but it would take one of the nicer electronic controllers, a high end regulator/meter for the co2 tank, and some figuring and R&D. I honestly don't know that it would be worth the cost and R&D for the results. With the bigger grows, a 10-15% improvement can mean big money, but in smaller grows, that much improvement may not be much and wouldn't be able to pay for itself.