You need to create the model driven app for accounts designated as referrals.

When the account is entered into the system, extra fields must appear if the referral customer box is selected. If the box is not selected, the extra fields must not appear.

Note: By combining conditions and actions, you can do any of the following with business rules:

Set column values

Clear column values

Set column requirement levels

Show or hide columns

Enable or disable columns

Validate data and show error messages

Create business recommendations based on business intelligence.