Stencyl uses Caurina's Tweener. When adding a tween, you have the option to provide a callback to know when the tween is done.
I'm attaching an AS3 soruce file as an example of how I handle tweens. In particular, the the example uses tweening to move an actor. Due to timing issues, the final position of the actor may be off by a couple of pixels (quite bad for low-res games), so I use a callback to precisely palce the actor when the tween is done.
Note that you don't need to use bitwise operations to keep track of tweens. I happened to do it that way because of an assignment (they're handy if you have plenty of tweens to track though).
