How can I harvest Auto-Reply (Out-of-Office) text for all accounts on our network (Outlook 2010)

I develop small applications in house with VBA for MS Office - mostly Excel/Word and only recently Outlook.

I have been asked if I can create an application that consolidates information from Outlook and elsewhere so that our admin staff can, on a single screen, track the planned location and activity of all our staff for the current day.
I have more or less resolved how to harvest calendar data via shared calendars. However, our employees are very varied in how they use Outlook. Their 'Inside My Organisation' auto-reply is a useful source of information that I would like to exploit.  I cannot see any obvious means to access the auto-reply text via the Outlook object model.

 I suppose that I could implement a horribly complex scheme that programmatically generate a daily email to each account with a rule on each account to respond if the mail is an auto-reply - then analyse the responses.  This would be intrusive to users, cumbersome to implement and may have pitfalls that I have not yet foreseen.

I note that when creating a new email to a colleague who has Auto-Reply turned on I see their Auto-Reply message displayed at the top of the e-mail.  Is there any way that I can leverage this or, another method in VBA, so that I can harvest all of the Auto-Reply messages (Inside My Organisation) for the accounts on our network?

Alternatively, can this be achieved with some code running on Exchange Server - if so any general pointers as to how to do this would be appreciated.