For starters, grab TweenLite instead of the Adobe tweening - it's much more reliable for this kind of work. With that included, you can use the same formulas you have now, just pass them into the tween:

PHP Code:
import com.greensock.*;
import com.greensock.easing.*;

// ...

TweenLite.to(fermez.x1, {x:fermez.stage.stageWidth fermez.width 30ease:Elastic.easeOut});