Using formulas (and more) in forms

Hello,

I would like to make a “batch preorder form” where customers can see a list of items (with prices), and pick the quantity of each item they want to preorder, with with the total bill being update while they fill the form.

Is it possible?
That would replace the current workflow, where batch preorders are organized by sending excel files by email.

I’m still a neebie, but so far I found no example of

  • dynamic content or formulas displayed in forms
  • static variables (like the price in my example) displayed in forms
  • non-trivial forms where there is no 1-1 mapping between form questions and table columns (for instance, would it be possible to fill this invoice example from a form?

Is there some example or documentation that I missed?