We will write this custom function in Zoho Books, which is the center piece of the Zoho Finance Suite. You can also write functions in Inventory, Expense, or Invoice, if you use those separately, but this course works out of Books.
One thing we hope to update when Zoho fixes it: if you need the same function to run in Books and Inventory, currently you have to copy/paste and create the function and workflow in both places for it to work.
