Executing Lectora actions/variables from Captivate 4

Using a button Flash CS4, I have successfully managed to execute actions in Lectora using an embedded swf (not HTML object) (Actionscript 3.0) with the following call:

ExternalInterface.call("action164");

When I try to use the "Execute Javascript" in Captivate 4 with the same call (using Actionscript 3.0) for a button's "on click" I get the following error in IE 8 on publishing the lectora file-

Message: 'ExternalInterface' is undefined

Have I missed something fundamental about Captivate's Javascript execution? I've been using Captivate for quite a while, but have until recently, not used the Javascript functionality as I've only just started using Javascript calls with Flash files.