IPTABLES Rule on Actiontec to Redirect DNS Traffic to OpenDNS

Hello,

For security, I would prefer to use OpenDNS servers instead of the Telus DNS servers. I have changed the DNS servers in the Advanced Settings admin page in the Actiontec modem gateway. However, some devices in my home (I.e. Chromecast) are configured to only use Google DNS servers (8.8.8.8). This is hard coded in the firmware and cannot be changed. I would like to create a rule in the Actiontec that forwards all DNS traffic on port 53 to the OpenDNS servers that I specify. In my previous Asus router, I was able to type this command in the terminal to accomplish what I needed:

iptables -t nat -A PREROUTING -p tcp --dport 53 -j DNAT --to-destination DNSSERVERIPADDRESS:53

replacing DNSSERVERIPADDRESS with the IP that I specified. How can I apply the same configuration in the Actiontec? Thank you in advance.