Help Using Server.MapPath - Physical Path

Im displaying the contents of a folder on a web page.
I have the following line :
Dim dirInfo As New DirectoryInfo(Server.MapPath("~/published/info/"))
This works fine at the moment (as im developing the page).  When the system is live the published/info folder is outside of the root of the application eg:
http://mainserver/infoweb/info
the path of my application is :
http://iweb/
How can I reference a folder outside of my application using Server.MapPath?
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