Pop up reminder for "completed by date" in work order form

Not every work order requires a due date/completed by date, so having the field be mandatory wouldn't work. But we get a lot of work orders where there should be a completed by date on them, but they often forget. I'm proposing a pop up "Did you want to add a completed by date?" if they leave the line empty on work orders. That way if they meant to and forgot it'll remind them to add it. Saving us from having to go back and fourth with the requestor.