How to iterate through sub-workItems in a Workflow Rule?

Hi Support,

I am looking to define some workflow rules to automate some updates to project sub-items we are currently doing manually, but I don't see how to iterate through the project's sub-items.  I have reviewed the documentation on http://usermanual.clarizen.com/#clarizen-functions but don't see anything there that would allow iterating through the sub-items.  Am I looking in the wrong place?  Appreciate if you could provide an example.

Thanks,

Richard