Scrollpane component

i have a scrollpane tha tlinks to a movieclip. it loads the movie clip just fine, but when I change the data in that movieclip, the scrollbars don’t adjust. as in, if there is a small amount of data in the movieclip and there are no scrollbars, and then the movieclip doubles in size, the scrollbars don’t appear. How do i get them to adjust?