Hola como estas, tal vez sea esta la Api q me decis:
Saludos.
Código [Seleccionar]
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Private Const CB_DIR = &H145
Private Const DDL_ARCHIVE = &H20
Private Sub Command1_Click()
Dim path$
path = "c:\Carpeta\*.*"
SendMessage Combo1.hwnd, CB_DIR, DDL_ARCHIVE, ByVal path
End Sub
Saludos.