Worrying about what my colleagues would think of me if I didn't have at least a glass of wine in hand, is what ultimately saw the end of my 3 year sobriety and the beginning of a 3 month relapse back into Hell.
My advice: prepare ahead of time if you know you are going to be around alcohol. "No thank you" is perfectly acceptable as a response and nothing more need be said.
In fact, I remember going to work dinners and being the only one not drinking, gave me a sense of pride.
Happy you didn't give in. For all you know, that drink could have been the beginning of the end.