請問vb高手，如何在檔案總管中，將1022檔案之內文，批次加入同三個字？ 如「本回完」？謝謝！?

Imports System.IO

'...
Dim fileEntries As String() = Directory.GetFiles("C:\novel", "*.txt")
Dim fileName As String
Dim buffer = "End of chapter"
Dim sw As New IO.StreamWriter(fileName, True)

For Each fileName In fileEntries
    Try
        sw.writeline(buffer)
        sw.close()
    Catch ex As Exception
        MessageBox.Show(ex.Message)
    End Try
Next
'...
'沒試過，用前請先隨意拿個不要的txt檔作測試