I use Wateen WiMax and I wanted to share internet between my computer and laptop over Bluetooth.
It was not an easy job. It cannot be done by Windows Internet Connection Sharing (ICS)  But finally I figured out a way to do it.

You have two computers with Bluetooth
Computer 1 has internet connection
Computer 2 You want to share internet connection with.

1. Install a proxy server on Computer 1. I used ezProxy.
2. Join two computers by Bluetooth Personal Area Networking (PAN).
3. On computer 2 go to Tools > Internet Options > Connections > LAN Settings.
Check use a Proxy Server for your LAN box.
4. Give IP address and Port Number assigned to Proxy by Computer1.
5. Enjoy surfing net on Computer 2. Happy Browsing