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:
If(field1.rawValue == null || field2.rawValue = null || field3.rawValue = nul){
pop up a message box telling user they need to complete the fields
setfocus back to the section
}