Scrape supplier Excel stock levels & sync with my stock sheet

Project Requirements:

Data Upload and Integration:

Allow uploading of our latest Shopify stock export file (XLS) and the stock data files from various suppliers. I also need to update a second file in a different format for Google and mark each product in a particular column with either the text 'in_stock' (for items in stock of with a known ETA, or 'backorder' where the item is out of stock and the ETA is not known.)

Stock Level Analysis:

Process the uploaded files to check and scrape stock numbers or estimated time of arrival (ETA) for out-of-stock items.

Stock Update Mechanism:

Update a column in our Shopify export file with predefined status messages based on availability:

- In Stock: 7-14 day delivery
(for suppliers' items that are in stock)
- Stock Due Imminently: Delivery within 2-4 weeks
(for suppliers' items that are due to arrive back in stock soon)
- Stock Due {Early/Mid/Late} {Month}: Pre-order today to secure yours
(to encourage pre-orders for items due back in stock at a known future date - the data in {} here should reflect what the stock sheets are advising)
- Out of Stock: Please get in touch for a pre-order discount
(to offer incentives for pre-orders when items are out of stock)

The updated Excel file should be ready to import back into Shopify to reflect the changes in stock levels.

End Goal:

To streamline our stock management process, making it more efficient and less prone to errors due to software instability.

Requirements:

A robust app that doesn't crash, works on Mac or online if possible (or Windows if it can't be done another way), graceful error handling that picks up any expected syntax changes in the supplier sheets, and shows a pop-up at the end telling me how many products have been updated. Also good documentation to help us use the app.

I have attached a screenshot of my current app, which needs replacing.