how to identify page in global.asax session and application start

I have a website with 2 possible start pages. how do you tell which page was invoked in both the session start and/or application start. when starting from the vs2008 debugger the first code I see executed is in session_start not application_start. should I assume it will be session_start and not application_start when the page is invoked from IIS? when I need to execute different logic based on the starting page, it would seem application_start is the right, logical place to do that, as opposed to session_start
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