yes that makes sense. When the user gets to the first field on section E you would need to trigger a validation on that fields On Enter event to set up a message if the fields are empty. There are several ways to do this depending on how complex section D is. If there are only a couple fields you could do something simple like:
Thank you for your response. A form has few sections, say for example Section A to Section K. Each section in a different page. Section D is more important than other sections. If the user does not provide answers any one of the questions in Section D and he moves on to the next section promptly he should get a popup alert like, "This is mandatory to fill all questions in Section D".
Hope it is clear and you will reply soon. Thank you.