Sub Macro2()
Dim aRng As Range
    Set aRng = ActiveDocument.Range
    With aRng.Find
        .ClearFormatting
        .Text = "Section"
        .MatchWildcards = True
        Do While .Execute  ' Loop until Word can no longer find the search string
            aRng.MoveEnd wdWord, 2
            aRng.MoveEndWhile "0123456789."
            aRng.Start = aRng.Words(2).Start
            If aRng.Fields.Count > 0 Then    'there is a field
                If aRng.Fields(1).Type = 3 Then aRng.Font.ColorIndex = wdBlue   'wdFieldRef=3
            Else
                aRng.Font.ColorIndex = wdRed
                ActiveDocument.Comments.Add Range:=aRng, Text:="Missing cross-reference field code"
            End If
            aRng.Collapse 0      'wdCollapseEnd
        Loop
    End With
    Set aRng = Nothing
End Sub