TweenLite.onOverwrite

[static] A function that should be called when any tween gets overwritten by another tween (great for debugging). The following parameters will be passed to that function:

1. overwrittenTween : Animation - the tween that was just overwritten
2. overwritingTween : Animation - the tween did the overwriting
3. target : Object [only passed if the overwrite mode was "auto" because that's the only case when portions of a tween can be overwritten rather than the entire thing] - the target object whose properties were overwritten. This is usually the same as overwrittenTween.target unless that's an array and the overwriting targeted a sub-element of that array. For example, TweenLite.to([obj1, obj2], 1, {x:100}) and then TweenLite.to(obj2, 1, {x:50}), the target would be obj2.
4. overwrittenProperties : Array [only passed if the overwrite mode was "auto" because that's the only case when portions of a tween can be overwritten rather than the entire thing] - an array of property names that were overwritten, like ["x","y","opacity"].

Note: there is also an onOverwrite special property that you can apply on a tween-by-tween basis like TweenLite.to(... {x:100, onOverwrite:yourFunction}).