Script to Change Subnet & Default Gateway for windows Server 2k8

hi,

We plan to change our network design and we want to run a script that will make things faster for us.

We want the script to run with the following conditions:
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1. It will keep the current Static IP Address that is configured and use it [it will not change].
2. Change the subnet mask to a new subnet mask we'll insert it.
3. change the default gateway address to a new address we'll insert it.

for OS: Windows Server 2008

we want that the script will be fully automatic (without the need to answer any questions).

thanks.