Actionscripting a tween

I have a movieclip that is a menu window that “opens” relative to the mouse position. What I really need is for the movieclip to adjust from whatever position it is in to a set position on the screen. when it is clicked on. I can get it to jump to the position but what I would like to do is for it to smoothly move as if it was an animation tween. How can you do this with actionscript?