Communication between Outlook addin and Program Automating Outlook

Question

I have an application that uses the automation interfaces to Microsoft Outlook to create a mail message and then after it is sent save an archive of that email message in my application.

I am hitting issues with a number of the third party encryption addins because by the time the Sent event fires what is passed to me is the already encrypted message.

I would like to somehow have them fire the event directly without sending a message to pass me the unencrypted version or I would like them to be able to somehow fire an event to me that passes the unencrypted message in a loosely coupled fashion.

I can't seem to find a way to define new events on the Outlook application object so I am looking for other ideas.

We capture the built in send event like this:

OutlookApp.ItemSend += new Microsoft.Office.Interop.Outlook.ApplicationEvents_10_ItemSendEventHandler(OutlookApp_ItemSend);

Thanks!