Movement using actionscript

How can I move a movieclip when a button is clicked, tweening it?

I can change the position of the movieclip successfully. But I can not figure how to animate the coordinate change!

Here is the basic actionscript…

on (release) {

This moves the movieclip (allBags) to _x=10.5
THen I have a button that moves the MC to -100.5

How can I tween it?