What you are describing is a MAPI information store. To write one, you'll need to use the Extended MAPI library and C++ or Delphi. See http://www.outlookcode.com/d/mapi.htm This is an advanced programming project.

--
Sue Mosher, Outlook MVP
Author of Configuring Microsoft Outlook 2003
http://www.turtleflock.com/olconfig/index.htm
and Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers
http://www.outlookcode.com/jumpstart.aspx

"Sebastian Gingter" wrote in message ...
I've been given a customer address database.

Now I should write a data source that brings this contatcs from the database
into outlook (like the personal address book).

I never developed an office extension so I absolutely have no idea where to
look first.

Can you please give me a hint at where to look first to make such a addon
for Outlook and what time/effort that would be to implement in average (just
for enabling outlook to pick a adress out of the lot), so that I can get a
rough overview about the task?