What can you do at a cocktail party if on diet?

Diet soda: Ah, my perennial problem! i give at least 2 lectures a week and always get invited to the cocktail parties. My solution is to have 1 drink, then ask for a club soda with lime, which everyone assumes is a gin & tonic. And i avoid those little platters full of snacks - each tidbit is about 1, 000 calories. Low-cal alternatives are always available, if you seek them out, or ask.