Sub HiSpell()
  Dim aRng As Range, aWord As Range
  
  Set aRng = ActiveDocument.Range
  aRng.LanguageID = wdEnglishUS
  aRng.NoProofing = False
  
  For Each aWord In aRng.Words
    If CheckSpelling(aWord.Text) = False Then
      aWord.InsertBefore "##"
      aWord.HighlightColorIndex = wdYellow
    End If
  Next aWord
End Sub