Sub Macro1()
Dim oRng As Range
Dim oPara As Paragraph
Dim i As Integer
    If Len(Selection.Range) = 0 Then
        MsgBox "Nothing selected", vbCritical
        Exit Sub
    End If
    For i = Selection.Paragraphs.Count To 1 Step -1
        Set oPara = ActiveDocument.Paragraphs(i)
        If oPara.Range.Style Like "Heading #" Then
            Set oRng = oPara.Range
            oRng.Collapse 0
            oRng.MoveEndUntil Chr(9)
            oRng.End = oRng.End + 1
            oRng.Collapse 0
            oRng.Text = vbCr
            Set oRng = oRng.Next.Paragraphs(1).Range
            oRng.Style = "Normal"
        End If
    Next i
lbl_Exit:
    Set oPara = Nothing
    Set oRng = Nothing
    Exit Sub
End Sub