Calculate Total Volume , Total Net Weight and Gross Weight in Sales Order

Hi All,
Based on the client business process we have to calculate the total volume, total Net Wt, and Gr Wt in sales order (When updating the qty of the item).

I have created the following
Filed type : User Input
Net Wt
Gr Wt
Filed Type: Calculated
Volume: I was able to calculate the value

Now, I want to calculate the total volume and total net weight in sales order (have created these fileds in ‘Sales Order’).
Q: How to bring values from another doctype to sales order
basically each item in sales order qty * volume of the item ;