Using cluster in node.js "worker" script

I have read every post and tutorial on cluster that I could get my hands on and they all "listen" for work to do from an http request (typically). Well I have a node script that does some work on the server, sleeps, then tries again. Basically like a cron job (except I'm using forever). So, no inbound http requests, no listener, it's not even a server. I ported the operation from a PHP script that ran in cron.

So how would I leverage cluster with a "worker" script such as that?

Tanks.