How can I do this using AsusWRT?

[UltrashRicco]

I

I cannot thank you enough for this. It seems to work great!

You might want to check the service-events script that would run your script at every reboot and everytime the firewall is restarted, instead of a crojob to run your script every minute. It worked well for me to enforce my DNS blocking rules.

But no need to fix your setup if it is not broken!