Couldn't find anything about this, tried to add the DNS name (which has like 100 IP's addresses) as a source address and it didn't like it ... seems like there may not be an option to use a DNS name instead of an exhaustive list of IP addresses for the Firewall rules?
If not, I assume the same would hold true for the Port Forwarding, if we can use a DNS name in the Firewall, then I guess we can't use one in the Port Forwarding either, right?