Thanks for the response.
Can't do it either...coz all users are Administrators. I need to do this because sometimes the DHCP leased IP addresses has reached maximum number. This happens when guests, customers, or clients plug into the office network using their laptops. And that makes me think to stop using automatic generated IP from DHCP and switch to static IP. However, this won't stop them to still plug into the network, but at least they must ask for permission to get an IP to connect to the network.

But there is still one more problem with using a static IP. Users can easily change their IPs to a known IP of their colleague's. This, of course, can cause a problem for the user whose IP had been stolen.
So, any other suggestions to solve my problem?