Class interaction

I have a control called "A." Control A has a private reference to a collection class called "OBJECTS" The Item property of the "OBJECTS" collection is an "OBJECT" class. How can I notify the "OBJECTS" collection when a SINGLE item of the "OBJECT" class is modified and which item it was.

For example I have a control that has a clsButtons object which is a collection of clsButton objects. If the caption of a single button is changed, I just want to refresh that particular button...not the whole control...ideas?