That might work. There is some documentation about how to poll Active Directory for changes to entries:
http://msdn.microsoft.com/en-us/library/ms677626(VS.85).aspx
and
http://support.microsoft.com/kb/891995
I have a python-ldap script that implements support for the DirSync control - http://github.com/richm/scripts/tree/master/dirsyncctrl.py