risolto con:

codice:
Dim fso As FileSystemObject
Dim f As Folder
Dim ff As Folders
Private Sub Command1_Click()


Set fso = New FileSystemObject

Set ff = fso.GetFolder("c:\").SubFolders

For Each f In ff
   ' Debug.Print f.Name
   List1.AddItem f.Path
Next
End Sub

Private Sub List1_Click()
Set fso = New FileSystemObject

Set ff = fso.GetFolder(List1.Text).SubFolders
List1.Clear
For Each f In ff
   ' Debug.Print f.Name
   List1.AddItem f.Path
Next
End Sub