Hi
Not sure what you mean. Do you mean that you don't want any of your users to be able to change the IP address that they have been assigned by the DHCP server.
What are you worried about them changing their IP address to.
There are a number of things you can do at the network level but a clearer explanation would help before we suggest solutions.
Also be aware that one of the most effective ways of stopping users manually changing the IP address is to lock down access on the desktop which is an OS and not a network issue.
Please elaborate
Jon