Scrolling gallery (easing help!)

ok, ive worked with the scrolling menu tutorial, and the infinite menu tutorial, but thats not what i need:
i have forty images all the same size, perfectly next to eachother that makes one long horizontal mc. now i want only two buttons (forwards and backwards) so that when you click the forward button the movie clip slides to the next image, but only moving the mc the exact witdth of the next image. i want to keep doing this by using only the forward or backwards buttons? not sure if im making myself clear, but…

something like this

thanks very much!;(