Request: Outlook Add-in event handlers for changes to Subject and Body text

As developers of an Add-in that helps users to file messages into document managements systems and other storage, we would like to be able to respond to changes to the message, as our Add-in suggests where to file a message based on its content. So we need to know when the content has changed.

Ideally we would like to have separate event handlers for changes to the Subject line and the Message Body.