To be short: you can not open Outlook calendar from a web application, not from client side, and even less from server side. There were methods that could be used with ActiveX from Internet Explorer, but newer IE versions have closed those security holes. You should not try to solve this by client side means. And Outlook is on client side. It won't work.
But you can access the Exchange server (the one that is actually storing the calendar) via the Exchange Web Service from version 2007 on. Look here:
http://msdn.microsoft.com/en-us/uc14trainingcourse_5l_topic2.aspx[
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If you have Exchange version 2003, you still have some possibilities:
http://stackoverflow.com/a/878299[
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