Sub HeadsTransformReverse()
  Dim i As Integer
  For i = ActiveDocument.Paragraphs.Count To 2 Step -1
    TagRange ActiveDocument.Paragraphs(i - 1).Range, ActiveDocument.Paragraphs(i).Range
  Next i
End Sub

Function TagRange(rng1 As Range, rng2 As Range)
  Dim i1 As Integer, i2 As Integer, rngTag As Range
  If rng1.Text Like "<S#>*" And rng2.Text Like "<S#>*" Then
    i1 = CInt(Mid(rng1.Text, 3, 1))
    i2 = CInt(Mid(rng2.Text, 3, 1))
    If i2 = i1 + 1 Then
      Set rngTag = rng2.Duplicate
      rngTag.End = rngTag.Start + 4
      rngTag.Text = "<S" & i1 & "-" & i2 & ">"
      rngTag.HighlightColorIndex = wdTurquoise
    End If
  End If
End Function