Hi there,

I'm trying to create custom function which auto-fills custom modules date by 

referring deal's date.

We're running a photo studio and there are some rental clothing (custom module).
What I want to achieve here is when we create shooting details (deals) and set rental clothing as related list, 

the function auto-updates rental date in custom module's date by using pre-made deal(shooting)'s date.

I'm sorry but I'm totally new to Zoho CRM&Functions and asking basic question.
Hope somebody give us an advise.

Thank you,

Yu