Import a bunch of IP addresses

We have a custom list of about 600 or so IP addresses we would like to block and wondered if anyone knows of a way to import all of them to a network group or other way to get them in a list so we can block at the firewall.

Any info would be helpful as I checked and I don't see of any easy way to do this and also looked in the forums for a way to get this done and so far turned up nothing.

Thanks,
Chad