Is there anyway for us to auto-populate under a Subform inside Zoho CRM?

I wanted to have that process executed when an update or a new entry is made on a specific field. But I'm not sure how to do that since I can't find one function under the Workflow Rules unless I dive in deeper to create a function of my own.

Please help.

P.S. If we do have a template or a sample for that solution, it would be nice.