I do not know what you mean kill the network. If you are talking about a single computer to be on or off a network there few creative ways to deal with it.
You can make a Release batch file like ipconfig /release (this release the TCP/IP stack) and a renew file ipconfig /renew and let it run according to schedule by using one of the automate type of programs that are available.
If your need is Internet related there are Kids Internet control applications (like Net Nanny) that can do this as well.