How I would make it read-only, so no one can modify?

Hello,

This is fine, how I would make it read-only, so no one can modify the calculated field?

You can set the form calculation widget as read-only in the widget settings. Here's how:

1. In the Form Builder, select the form calculation widget and then click the "Widget Settings" button. In the widget window, click the "other" icon.

2. Go to the "Options" tab and enable the "Result field is read only" option. Click "Back" and then "Save".

Hope that helps. Thank you.