I have an app that basically acts a price calculator where the user adjusts the quantities for any of 400 items, and a total price is calculated. I don’t want the app ever to sync to the spreadsheet, I only the spreadsheet to sync to the app. This is...

I have a very basic price app that runs way too slow. Its a simple price list with about 400 items, a price for each item, and a quantity that the user changes. The app them multiplies the quantity by the item price and calculates a total. It’s like ...