Declaramos en el formulario la función :

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

Y enviamos un mensaje al listbox :

dim i as integer
i = SendMessage(List1.hwnd, &H194, 200, ByVal 0&)