Does anyone have a recipe for a low-cal Margarita?

I really, really want to reduce my intake of sugar. I’ve done well with that, but I still have a penchant for the lovely Margarita. I have tried using diet lemon-lime soda pop as one webcipe suggested, but it was not at all good. It would seem that a diet Triple Sec would be the fix but I cannot find one! Any one of you flutheraholics got any ideas?