Script writing

I am administering a LAN and one of the duties I have to perform is to upgrade the Antivirus software to prevent my network from computer virus.

Question:

How can I write a script that will be saved in a server so that when I uprade the Antivirus software in it, all the users who log in that server will automatically be replicated with the new virus definitions so that their Antivirus software will be automatically upgraded. (The Antivirus software that I use in my LAN is Norton 2000)

Yours,
Network Administrator.