combo box auto dropdown

Hi Folks
Does anyone know how to make a combo box drop down displaying its contents, with a call to the API?

Cheers

[CODE]
Option Explicit
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

Private Sub cmdopencbo_Click()
SendMessage cboonoff.hwnd, CB_SHOWDROPDOWN, 1, 0
End Sub
[CODE]

Cheers C