I think this is a wonderful suggestion. I also "give" myself a diet pop at restaurants as a treat and I have received regular pop a few times in error. Unfortunately, it is too late when you realize that it isn't a diet pop.

I find that this usually happens to me at the restaurants that provide you with free refills. I am going to try this when I go out. I have a good relationship with the waitresses at the restaurants I go to and I think once they realize the importance of diet over regular they will be more carefull in the future.

Thanks for the tip