VB Code:
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Integer, ByVal lParam As Any) As Long
private Const CB_SHOWDROPDOWN = &H14F
'to show the drop down:
dim lngRet as long
lngRet = SendMessage(cbo.hwnd, CB_SHOWDROPDOWN, -1, "")