onTweenComplete function...any way to trigger something half-way through a tween?

Hi

I have two boxes. Box 1 moves down the page and Box 2 up the page. I can get it so, after box 1 has moved down and reached its destination, box 2 is then triggered and starts its tween up the page. I am using MC Tween and onTweenComplete();

easy enough

But I would like box 2 to start moving, half way through box 1’s tween, so when the tween is only 50% complete…any ideas on doing this???

how can I constantly keep track of box1’s position? So a value is being returned like every millisecond to see if it has passed, say ._y>100…any ideas??? thanks