Red Tag Area Inventory

Hi! I am relatively new to Airtable so I apologize if my question is simple.
I have created a Red Tag Area table with all items in an inventory list.
I have a tables for “Inventory”, “Withdrawl”, and “Deposit”.
How can I create a running total for my inventory quantity column

Process for the table:
person wants to take 5 lamps out of the Red Tag Area
goes to “Withdrawl” table, fills out info, and puts “5” on “Quantity Needed” column
inventory quantity column in the “Inventory” table reduces by 5