Determine who has read a mail in shared mailbox

I'm thinking about a possibility to determine who has read a mail in a shared mailbox at Outlook 2010.

Of course a MailItem don't hold a property like "readBy", that's why I'm looking for a way to respond to the fact that a message has been marked as read. Then i could write the curent user name to a userdefined Field.

My first idea:

Listen to MailItem.Read() or MailItem.Open() with a VBA macro, but - when I'm not wrong - MailItem.Open() is thrown when a MailItem is focused and shown in the reading pane. If Outlook don't mark it as read automatically, the Info "Read by Max" would be wrong. MailItem.Read() is thrown only when a MailItem is opened to a new window, but what's when i press Ctrl+Enter?

After some Googling it seems that VBA isn't able to solve this on a good way or is it? Should I think about writing an Add-In?

Do you have a idea how i could go about this?
Any thoughts would be greatly appreciated


Best regards