MTNL Broadband: Disable wireless access

[crackers23]

I have MTNL Mumbai triband broadband with wireless modem. I have a PC and normaly use broadband on my PC only thru LAN card.I have taken wireless modem since my brother should be able to access it once or twice in a week when he visits my place with his laptop. Can I diable wireless access completeley , when I am using broadband only on my PC and enable wireless when I want to use it on laptop ? Please guide me.