FreshTomato cron job to reevaluate DNS allow list in port forwards

I have a router running FreshTomato using DDNS addresses for the allow list on my port forwards. This works well except that when save is pressed on the port forwards screen the DNS address is resolved to an IP address and cached. Is there a command I can run on the router from a cron job to reevaluate these DNS addresses so my forwards continue working when my DDNS updates?