Anantha,
I do not have a script for this, However, I think you should look at the following commandlets to do this.
Get-NaNfsExport
Add-NaNfsExport
Set-NaNfsExport
Remove-NaNfsExport
I think you will ned to get the rule for that path and then parse the IP's and creatre a new set of IPs. You can then set the rule with the new IP's. Pay attention to the -persistant flag if you want to update the /etc/exports file/
Mike