Sub main()
Dim p As String
'対象ﾌｫﾙﾀﾞを指定してください｡
'このﾌｫﾙﾀﾞに この実行用のﾌﾞｯｸは 入れないでください｡

p = "C:\test\"

'処理対象となる拡張子を指定して 呼び出します｡
Call jikkou(p, "csv")

End Sub


Sub jikkou(p As String, s As String)

Dim bk() As String
Application.DisplayAlerts = False
 
Dim fdb() As String
 
a = 1
f = Dir(p & "*." & s, vbNormal)
Do While f <> ""
 ReDim Preserve fdb(a)
 fdb(a - 1) = f
 a = a + 1
 f = Dir
Loop



For aaa = 0 To a - 2
 k = 0
 ReDim bk(k)
 f = fdb(aaa)
 f1 = Left(f, Len(f) - 4)
 
 ch1 = FreeFile
 Open p & f For Input As #ch1
 
 Do While Not EOF(ch1)  'ﾌｧｲﾙの終端かどうかを確認します
 Line Input #ch1, textline  'ﾃﾞｰﾀ行を読み込みます
 ReDim Preserve bk(k)
 bk(k) = textline
 k = k + 1
 Loop
 Close #ch1
 
 ch2 = FreeFile
 Open p & f1 + "_softbank.txt" For Output As #ch2
 For i = 0 To k - 1

 textline = bk(i)
 flg = 0
 hai = 0
 moji = ""
 outf = 0
 For c = 1 To Len(textline)
 z = 0
 If Mid(textline, c, 1) = """" Then
 If flg = 0 Then
 flg = 1
 Else
 flg = 0
 End If
 z = 1
 End If
 If flg = 0 Then
 If Mid(textline, c, 1) = "," Then
 hai = hai + 1
 If hai = 6 Then
 If Trim(moji) <> "" Then
 If IsNumeric(moji) Then
 If CLng(moji) >= 1 And CLng(moji) <= 12 Then
 outf = 1
 End If
 End If
 End If
 Exit For
 End If
 z = 1
 moji = ""
 End If
 End If
 
 If z = 0 Then
 moji = moji & Mid(textline, c, 1)
 End If
 Next c
 
 If outf = 1 Then
 Print #ch2, textline  'ﾃﾞｰﾀの書き込みをします
 End If
 Next i
 Close #ch2
 
Next aaa

Application.DisplayAlerts = True

End Sub

これだけでいいです｡