Help me with Cron job code for Hosts file update !

Hi, i am looking for a cron job to do a regular update of the hosts file in my Tomato firmware for r7000.
i installed this Adblock: not so lean code, but i didnt get a simple instruction to follow the cron job for updating Hosts file, say for ex. at 2am every day or once in 3 days or so.

Can anyone here help me pls ?

Thanks in advance.