I believe this has been discussed before -- if not in this forum, the Notes 4/5 one -- so you might want to do a search. However, in terms of accessing this kind of info from a browser, I imagine one way would be using some kind of ActiveX control or with some kind of piece of VBScript in a web page.
Take a look at some of the .NET / VB sites out there, e.g.
http://www.mentalis.org/
HTH
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http://www.benpoole.com