Option Explicit
Sub test()
Dim Fso As Object, MonRepertoire As String
Dim f1 As Object, f2 As Object, wb As Workbook
Set Fso = CreateObject("Scripting.FileSystemObject")
MonRepertoire = "C:\TEST EXCEL\"
For Each f1 In Fso.GetFolder(MonRepertoire).SubFolders
For Each f2 In f1.Files
Set wb = Workbooks.Open(f2)
'tes instructions
wb.Close
Next f2
Next f1
End Sub