To create multiple appointments on irregular dates, you have three options:
1) Create the first appointment, then Ctrl+drag it to the other dates to
create a copy of the appointment on each of those dates.
2) Create a recurring appointment that comes close to fitting your schedule,
then drag those appointments that are on the wrong dates to the correct
dates.
3) Use the WS:Repeat Appointment tool from
http://www.websetters.co.uk/WSAddIns/Repeat%20Appointment/Index.htm to
schedule repeating appointments that do not fit a regular pattern.

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Sue Mosher, Outlook MVP
Author of
Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers
http://www.outlookcode.com/jumpstart.aspx
>I would like to set up a recurring appointment, but the frequency of the
> appointment is random (doesn't fall under the every week, bi-weekly,
> monthly,
> etc timeframe). Does anyone know if this is possible in Outlook 2003? Any
> help would be greatly appreciated.