Figurati ...

Comunque in VB6 si farebbe cosi'

codice:
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_SHOWDROPDOWN = &H14F

Call SendMessage(Combo1.hWnd, CB_SHOWDROPDOWN, False, ByVal 0)
Prova ad usarlo ... non so se funzionera' ugualmente ...