For custom workouts you will have to program in what you wan to do. You can find the directions to do this on their site or in the directions that came with the CT. It's kind of a pain in the ass but you only have to do it once.
However, for what you are talking about just know that you will have to crank up the pressure between the drum and tire. CTs have a tendency to be pretty slippy when you are dealing with high resistance. Thus, you will want to calibrate to close to 6, which it doesn't recommend (CT like you to be closer to 3).
Be careful what tires you ride when doing this type of workout. If you have a tire with a kevlar belt etc. (some kind of puncture resistance) it will blister very easily, probably in 30 min or less. I would recommend getting one of the Continental trainer tires.
Jimmy
Jimmy Archer
Pro Triathlete/Coach/Freelance Writer
http://www.jimmyarcher.com http://www.dirttri.com