Blocking access to a particular port

[boney]

Hi,

I would like to know if it is possible to block a particular port(for
eg: port 21) with the help of a Windows Script and that too just for a
particular period of time. This should then allow no access to tht port from
any machine within the entire network. What could be the ideal command that
would enable this goal? or if there is any easier way to do this, please
suggest that as well.

Thanks
Boney