Google Doc Stock Reduction

I have 2 documents that I would like to merge and get to interact with each other. 1 is a google doc (I have exported and named Google Doc Hoodies), this is a live document that the customer will use to input the order details. They will go into the ‘Template Sheet’ tab copy the sheet and then paste into a new tab. They will then copy and paste data from an excel sheet (example as John O Gaunt Order Form) into this Google doc and populate the fields. This will happen for every new PO they receive. Approx 10 per day.
Our sales team will then go through the google doc and compare it to the excel stock sheet Stock Hoodies and manually work out what stock we are holding here and what we need to order.
As you can imagine this is a very time consuming process, we want to be able to add the Stock Hoodies excel into the Google Doc Hoodies so that every time the customer inputs an order, the stock line on the tab for Stock Hoodies reduces based on what has been ordered, whilst keeping a running total at the top and a list of orders below. We also want it to populate a field on the order page to have a tick or just X as to whether it is customer stock or DTB stock and a total at the bottom so that we can work it out.
I have attached all the stock lines that could be ordered under FIZZ BREAKDOWN2023, this shows all the possibilities that the customer could ask for, some of which we hold on site and some of which would need to be ordered in.
I have also attached a step by step guide as to how we want it to work (Fizz Data) and also an example of how we imagine it will look Fizz Example. If you can let me know asap regarding this solution that would be greatly appreciated.