Is it possible to make code in actionscript-3 to parse the virtual directories that are constructed in the flash library? I mean that if i add a folder on the library of CS4 called 'graphics' can i write code that parse the elements of that folder in order to fill an array with folder's elements(which are BitmapData classes) ?
No, not as far as I know.
One way of looking at it is that the library is part of the fla file, the source document, and not of the compiled swf. Assets in the library that are not "exported for ActionScript" are not included in the swf. ActionScript doesn't have access to the library as such, there is no object in ActionScript for it.