Sub Get_All_File_from_Folder()
    Dim sFolder As String, sFiles As String
    With Application.FileDialog(msoFileDialogFolderPicker)
        If .Show = False Then Exit Sub
        sFolder = .SelectedItems(1)
    End With
    sFolder = sFolder & IIf(Right(sFolder, 1) = Application.PathSeparator, "", Application.PathSeparator)
    Application.ScreenUpdating = False
    sFiles = Dir(sFolder & "*.csv*")
    Do While sFiles <> ""
        'открываем книгу
        Workbooks.Open sFolder & sFiles
        'действия с файлом
        'Запишем на первый лист книги в ячейку А1 - www.excel-vba.ru
        ActiveWorkbook.Sheets(1).Range("A1").Value = "www.excel-vba.ru"
        ActiveWorkbook.Close True
        sFiles = Dir
    Loop
    Application.ScreenUpdating = True
End Sub

Sub AttachFile_test()    ' пример использования
   Filename$ = GetFilePath()
    If Filename$ = "" Then Exit Sub
    MsgBox "Выбран файл: " & Filename$
End Sub

Function GetFilePath(Optional ByVal Title As String = "Выберите файл для обработки", _
                     Optional ByVal InitialPath As String = "c:\", _
                     Optional ByVal FilterDescription As String = "Файлы счетов", _
                     Optional ByVal FilterExtention As String = "*.*" )  As String
    On Error Resume Next
    With Application.FileDialog(msoFileDialogOpen)
        .ButtonName = "Выбрать": .Title = Title:
        .InitialFileName = GetSetting(Application.Name, "GetFilePath", "folder", InitialPath)
        .Filters.Clear: .Filters.Add FilterDescription, FilterExtention
        If .Show <> -1 Then Exit Function
        GetFilePath = .SelectedItems(1)
        folder$ = Left(.SelectedItems(1), InStrRev(.SelectedItems(1), "\" ) )
        SaveSetting Application.Name, "GetFilePath", "folder", folder$
    End With
End Function