Customize error message when mandatory field is not filled by emp created in Application Composer

Summary:

When "Management Information" category is selected in Service Request, additional fields will be captured on creation page of Service Request which are mandatory. Now lets say employee raise a Request and selects some category other than "Management Information" and saves a Request. Now when an Agent opens an existing Service Request and change Category to "Management Information", in that case system will throw an error as additional fields added in creation page cannot be filled in Details page by Agent. Is there any way to customize error message when custom mandatory field created from Application Composer is not populated?