Flash CS4 Professional.
videoItem.sourceFileIsCurrent
Read-only property: a Boolean value of true if the file modification date of the Library item is the same as the modification date (on disk) of the file that was imported; false otherwise.
Assuming that the first item in the Library is a video item, the following code displays "true" if the file that was imported has not been modified on disk since it was imported.
var libItem = fl.getDocumentDOM().library.items[0];
fl.trace("fileIsCurrent = "+ libItem.sourceFileIsCurrent);videoItem.fileLastModifiedDate, videoItem.sourceFilePath