pi_iframe to non-http target

[djanelle]

This should be a no-brainer. I'm trying to use pi_iframe to link to a plain-text file on a Windows shared folder. I can get it to work when the target is a web page.....{pi_iframe url="http://whatever.com"} but what is the syntax for a target that's not http, like \\server\share\file.txt  I tried {pi_iframe url="\\server\share\file.txt"} but that doesn't work.