I have to do my pivot background frame by frame?

I have been working on it for a long time, and when it comes time to finish, i realize that i forgot the background! no problem right? WRONG. it won't do every frame at once, it's making me go through frame by frame, there is well over 3000 frames and i don't want to spend hours going through all of them!! I'm using pivot 3.1 beta.