I’ve been using the Fuse Kit and Zigo tween engine to write actionscript tweens. Pretty easy to use, lots of control when you move onto the Object Syntax. You can synch and sequence movie clip tweening of alpha, position, colour, rotation, scale and more.
If you use it, be sure to donate to Moses Gunesch who brought together all the goodness for this great tool to happen. The link is at the bottom of the page.