Accessing a Windows Share on another Server via HTTP scripts

I have a share on a windows 2003 server which I need to access via a script running on our web server. The script commands run without problem from the command line on the web server, but they fail when run from the web page. I assume this is something to do with IIS security or similar but am at a loss as to how to cure it.

Anyone know what I need to do?

Thanks