Hola
Para eso mejor que Shell puedes utilizar la API ShellExecute. Tienes que declarar la API
Código:
Private Declare Function ShellExecute Lib "shell32.dll" Alias "ShellExecuteA" (ByVal hwnd As Long, ByVal lpOperation As String, ByVal lpFile As String, ByVal lpParameters As String, ByVal lpDirectory As String, ByVal nShowCmd As Long) As Long
Const SW_SHOWNORMAL = 1
Luego para abrir la carpeta
Código:
ShellExecute Me.hwnd, "open", "D:\Misdoc", "", "", 1
Si quieres abrir la carpeta en modo explorardor en lugar de open pones Explore
--Saludos--