allocate specific floating ip for tenant

Hi, I have class C sub-net 255.255.255.0 for the public network. And, I want to only allowed tenant to use specific public IPs. I know how to limit the number of the floating IPs for each tenant using quotas, Although quotas does not allowed me to restrict the users to only use specific range of floating ips. Any idea how to set custom range of floating IPs for each tenant?