Consider scenario, where subtotal amount from several fields must be shown in a corresponding field.
Usually such field are made read-only, and are populated with data according on some function, that count data from corresponding fields and populates subtotal.
This article describes how to make field read-only.
Step 1. Prepare a template
Step 2. Choose Subtotal field and navigate to Properties → Enabled and set to No
Step 3. Publish the template.
Step 4. Runtime. Fields are empty and Subtotal field is read-only
Add several items to the table and specify cost
Subtotal field is auto populated and value cannot be edited, unless one of the Cost field are changed.