You could use a workbook event.
Rightclick on the excel icon to the left of File (on the worksheet menu bar).
Select view code and paste this in:
Option Explicit
Private Sub Workbook_BeforePrint(Cancel As Boolean)
Dim myRng As Range
Set myRng = Me.Worksheets("sheet1").Range("a1:a3,c9,d14")
If myRng.Cells.Count <> Application.CountA(myRng) Then
MsgBox "Please complete those cells!"
Cancel = True
End If
End Sub
Modify the sheetname and addresses to your liking.
(if the user disables macros or disables events, then it won't stop them. In
fact, if they copy the worksheet to another workbook or copy the cells to a
different worksheet, it won't stop them. But it should stop most.)