Motion tween

can someone please tell me how to make a motion tween of a graphic expanding, but ONLY TO ONE SIDE…i have a rectangle and i only want the right side to expand…but if i use the expand tool, it will expand evenly on bowth sides…please help…or tell me if you can do this at all…THANX

Move the center point of the graphic to the side that you want to expand (i.e. grab the center DOT and move it over to the left or right side of the symbol. Then the DOT will appear there instead)…then drag the expansion in that direction. I hope I explained this well enough…

thanx allot that helped