It has been years since I messed around with AS2 and Captivate 4, but as far as I remember if you insert an SWF in Captivate and call "_root" from this SWF, the _root element referenced is the Captivate movie.
Try something like _root._parent._parent - don't know if it will work, but you definitely need to get hold of the proper object before you can set any variables etc. in your framework.
www.cpguru.com - Adobe Captivate Widgets, Tutorials, Tips and Tricks and much more..