Most addins have passworded code. If not you can modify the registry to view them.
HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\PowerPoint\Options
Create or change DWORD "DebugAddins" value = 1.
(If this means nothing to you don't go there!)
Event handling is not simple. There'a fairly simple example in the Kbase on this site. Just as an aside the example is unnecessary as you can create a simple switch in the shortcut to do the same thing! If you have a particular event in mind we can easily create a template for the add in (not free but cheap!)
john AT technologytrish.co.uk