Establish a relationship between newly added fields (which are not custom fields) in a form

How can I establish a relationship between newly added fields (which are not custom fields) in a form and the primary field of the form in Dynamics 365 for Finance and Operations? For instance, if I’ve introduced a new field to a form where the primary field is “Item ID,” how can I ensure that these new fields are dependent on the “Item ID” for their functionality?