Flash CS4 Professional.
bitmapItem.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 the first item in the Library is a bitmap 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);bitmapItem.fileLastModifiedDate, bitmapItem.sourceFilePath