General :: Machine Act As Both A Wireless Client And Access Point Simultaneously Using A Single Physical WLAN Interface?

If I have only 1 physical WLAN interface, is there some hackery that can be done so that it can be a client of an existing access point and at the same time also act as an access point for other clients? I have an existing 802.11g ADSL router, and I'm going to be building an HTPC which will have 802.11n. My laptop also has 802.11n, but at the moment it only connects at 54Mbps because thats what the AP supports. I'd like to be able to have the HTPC be a client of my ADSL router, but have my laptop be a client of the HTPC, so copying files to it will be faster.