You can easily restrict the IP ranges by:
1. Go to Control Panel / Administrative Tools / Internet Information Services Manager
2. Expand the server and the web site node under it
3. Select the ensemble video web site and go to "Properties"
4. Go under the "Directory Security" tab
5. Click the "Edit" button under the "IP address and domain name restrictions"
6. Select "Denied Access" for "By default, all computers will be"
7. For each IP range in your spread sheet, click "Add", select "Group of computers" and enter the IP range and the subnet mask.