blocking internet from certain DHCP range

I'm trying to block internet from a certain DHCP range. That way the people that my manager doesn't want on the internet, I can just change them to DHCP and that's it.

I have a Fortigate 110c firewall. I know how to block the internet through UTM profiles, or just every website through a *whitelist from a specific IP, but how do I do it from a range of IPs.