If you mean on a BT Home Hub? and you have a version 2.0? Go to 192.168.1.254, choose, Settings, then choose Access Control.
Alternatively BT Home Hub 2.0s have a utility that allows one to switch the WiFi off entirely between set times. Its on the Home Page 192.168.1.254.
If you don't have BT Home Hub 2.0 try a NEW question with a lot more information about what you DO have.
T, December 2008
