Using a UNC path in ImageURL

I am using the following in an itemtemplate:

<asp:Image ID="Image1" runat="server" ImageUrl='<%# String.Format("\\servername\foldername\foldername\{0}.jpg", Eval("FacilityID"))%>' Width="250px" Height="200px" />
                         

The image does not show up on the page.  When I click on view Image, I get the following link http://www.website.com/\\servername\foldername\foldername\filename.jpg which obviously doesn't work.  If I take out the http part it works.  How can I get this to work?  This is an internal website.  Thanks!