Ms. Fine,

A warning here about those margaritas. As a liqueur, Triple Sec is like Cointreau and loaded with sugar - use with caution! I believe it has about 7 gr. carb per oz.

Crystal Light is a sugar free drink mix. It would make a dandy substitute for lime juice and lower carb too.

One other thought. Have you considered a beer and diet lemon/lime soft drink mixture? I had an English friend years back who it a shandy.

Cheers!