if you are still trying to work this out, can you elaborate on this:
" ...by just moving the mouse from one side to the other..."
and this: quote:
"...but how do you target a MC with a button ?...."
on the surface, i am sure what you want to do is easy enough, but it is hard to guess at from the way the quesstion is posed.
forget about 'buttons' ( i.e. 'simple buttons'). turn your images into movieclips. every movieclip is in effect a 'button', but without the simple rollover effect, which is easy to code on your own, with greater flexibility.
also, are the images to appear where the mouse is, or somewhere else? are multiple images expected from the same mouseover, or is there a one to one correspondence with an image and a 'button' ? that is unclear to me.