There is one way, Get a Wireless router with an internal firewall, use WPA for access from the wireless side and use packet filtering for access from the wireless side also.
This ain't great, but it 's a start. You can get wireless routers with decent firewall protection but your going to pay a 'little' more than the normal $50-100 for them. You need a business class router or enterprise router for a real good solution.
hope this helps,
Robert Smith Consulting Wired & Wireless Networks for Home, Business & Enterprise