When applying Public Access restrictions for pages in Umbraco, it would be helpful if we could restrict by IP address in addition to username/password.

Part of my site is an Intranet.  I'd like to be able to configure Umbraco so that if the user is within a specified IP range, they'd be automatically granted access.  If the user is from outside of the specified IP range (such as if they are at home), they'd be taken to the login page and allowed to gain access that way.