临时Internet文件（通过IE从SharePoint读取）。我如何找到URL？

When an IE user clicks the link of a file residing in SharePoint (and user selects "read-only" access), the file is copied to Temporary Internet Files, my application is opened and passed that filename as a parameter. I'm trying to implement a "check out" button in my app so that a user can switch from read-only mode to check-out and edit mode. I haven't been able to find a way to learn the SharePoint URL for the file. On check-out and edit, it's no problem: there's a registry entry that maps the file on my system to the URL in SharePoint; I haven't found anything like that for read-only files.When an IE user clicks the link of a file resid