[Zope] hopefully a simple hook

Hi, I was wondering if there was a simple hook into ObjecManager or something like this that lets me know when an item in the container has been altered. At present I have to actively mine the container for changes to bobobase modification times of the objects it contains. I have wrapped a small product around Folder.Folder to allow me to do this, but would like to find a hook that lets me know when the modification time of a contained object has changed. Matt