I thinking one app use form to register to buy products.
When user click button form register, will display one form and After they choose information such as: product, quantity to buy …, the form will report the amount equal to the unit price * the amount ordered before they click Submit? Or can they create an invoice preview function?
I don’t think you can do that natively within Glide. I tried creating a math column, but it will not update with a Form or Add/Edit mode.
What I would suggest is to let people ‘Add to a Cart’ by submitting a form for each purchase with a quantity entered. Then create a summary total in a Cart sheet somewhere else in your spreadsheet using formulas. The user can then view that cart sheet row in the app and the buy button can pull values from that row.
I have tried that, but the problem here is that in order to have that data, the person who needs to enter the form needs to select submit for the new data to be updated. However, when you choose to submit a new data, the user wants to change it, the invoice still shows them purchased twice if they change the number of products.
If they submit a form and they can view it in a list, then you can turn on editing for that record and they can change the quantity or delete the entry if they choose. Once they are happy with the list of items in their ‘Cart’, then they can select the buy button, which will take the sum of amounts from all the list items and pass it to Stripe.