How can i simply reload a movie clip once it has been unloaded?

i have 4 movie clips that overlap each other and i’m trying to hide 3 while one plays… so the button action i applied was:

on(release){
unloadMovie(“walkright”);
unloadMovie(“walkdown”);
unloadMovie(“walkleft”);
_root.walkup.gotoAndPlay(1);
}

so this would show the “walkup” movie clip and hide the other 3 MCs. it works fine, but then when another button is clicked to play “walkright”, the unloaded movie clip doesn’t want to come back. so how can i play one movie clip at a time while hiding the other 3? does this make any sense? thanks a LOT in advance.