Flash CS4 Professional.
document.sourcePath
Property; a string that contains a list of items in the document’s ActionScript 3.0 Source path, which specifies the location of ActionScript class files. Items in the string are delimited by semi-colons. In the authoring tool, the items are specified by choosing File >Publish Settings and then choosing ActionScript 3.0 Script Settings on the Flash tab.
The following example adds the ./Class files folder to the document’s Source path:
var myDoc = fl.getDocumentDOM();
fl.trace(myDoc.sourcePath);
myDoc.sourcePath = "./Class files;" + myDoc.sourcePath;
fl.trace(myDoc.sourcePath);document.externalLibraryPath, document.libraryPath, fl.sourcePath