I saw an example on your site that uses static constants for OverwriteManager, such as OverwriteManager.PREEXISTING:
TweenMax.to(mc, 1, {x:100, overwrite:OverwriteManager.PREEXISTING});
But I can not get my editor to autocomplete or recognize that OverwriteManager Class. I dug through the imports available in greensock, but did not see it. I am on version 12. I would prefer to use the constants over numbers, as I think that is good practice, but I don't know how to go about getting this to recognize. FYI, I am using Flash Develop, in case the problem lies there.