How to perform operation in form for new custom doctype?

Frappe Framework Print Formats
1

I create a new doctype with the name Sale Stock Report. Now, I need some code customization according to my requirement. I have a child doctype in it with the name SSR Product Detail.
Requirements:

  1. When I select the product in child doctype, it will auto get the price of that product which I was selected.
  2. When I enter the value of opening_stock and purchase it will aslo auto calculate the addition of both field in the next field total.
2

Continuing the discussion from How to perform operation in form for new custom doctype?:

http://0.0.0.0:8000/desk#Form/Sale%20Stock%20Report/New%20Sale%20Stock%20Report%201![Capture|690x209](upload://72o3inzZKXZbRFZUQzCJFGVKCnv.jpeg)

This is the view of doctype when i select the product it should auto show that price into the next fields. When I enter the values of opening_stock and purchase it will auto sum that value into the next field total.