Code to add 'ease' to this

Finally got the movement I needed :beam: …But can anybody add the ‘ease’ code to this? (think thats the right term…meaning to slow the movement down as it reaches it’s end position) =)

onClipEvent (load) {
//this sets the initial x position of our clip
this._x = 550;
}
onClipEvent (enterFrame) {
//this moves our clip 5 pixels to the right every frame until it reaches a certain point
if (_root.small._x>550) {
_root.small._x += -20 ;
} else if (_root.small._x>200) {
this._x += -20 ; _root.small._x += -20 ;
}
}

last bit of help needed!!! Wahoooo (well…for now!)