Hi,

how about adding a method to the
collection class, which you call
when an object is added to your collection ?

In this method you can add a standard property
to the objects to be added (if it is not there already -
it should be there by way of inheritance if using your objects)
and filled with a reference to the object
where you want to call the specific new behavior.

I wouldn't use the collection itself,
but an object of it - coupling should probably
be loose here.

hth

thomas