Not using the Outlook object model, unless you're running on Outlook 2007.
To set OutOfOffice you would have to set the MAPI property PR_OOF_STATE
(0x661D000B) to False. That property is located in the default Store object,
in its Fields collection.
To set the OutOfOfficeText message you would set the text in a hidden
message in the Inbox with a MessageClass of
PM.Note.Rules.OofTemplate.Microsoft. The message text is the Body of that
hidden item.
If you aren't running Outlook 2007 you'd have to access that property and
hidden item using a low level API such as CDO 1.21 or Extended MAPI (C++ or
Delphi code only) or Redemption.(
www.dimastr.com/redemption).
