When you customise Outlook using VBA your code is added to a VBA project in the VB editor.
You cannot record macros in Outlook
You must write the code directly into the editor.
You can write your code in the ThisOutlookSession code module and you can add new code modules to this VBA project.
Using the ThisOutlookSession code modules gives you access to a number of application events where you can create event handlers and write code to handle different events.
This is a new feature in 2007 allowing you to create forms that appear within an Outlook Inspector
This can be created from VSTO 2005 SE
Open Outlook (Tools > Forms) click Design a Form
Select Message and click Open