Diapers changes & Tantrums?

How do you handle these situations?  B is usually okay with diaper changes, but you know how their moods can change from day to day!  This morning she absolutely threw a fit and thus, so did I.    It is hard for me to keep my cool sometimes when we are on a tight schedule, and you have to get through the "have-to's" !! 

I've been looking at advice articles and they all say to keep your cool and be calm with your toddler.  Yeah right, if only it was that easy!!  I can work on staying calm, but that's not going to prevent her from making it impossible to change her.  The only thing I can think of right now is bribing her with a snack.