FileSystem Access To Network

I want to write a script that can read and write files to a place on a network file-server. Since the machine-local IUSR is not a domain user, it cannot access the resource.I want to provide IUSR limited access to a particular place on the file server.

Can anyone help me think of a reasonably secure work-around to this issue. We tried creating a virtual directory that points to the share(using a domain account), but even then, site users can see the files (no security), but the fso (IUSR) cannot (no
functionality). There must be a way.