Block sites accessed by it's IP address

How would one go about blocking URLs that contain an IP?

Example:

hxxp://www.ok-website.com = good
hxxp://64.50.50.123 = blocked (unless added to exceptions)

I have tried using the "Block Uncatagorized" option but, that does not work in this case and is really quite unwieldy in general.

Gateway: ASG320
Firmware: 8.301

Thanks in advance.