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_SELECTSTRING = &H14D
Private Const CB_SHOWDROPDOWN = &H14F
 
Private Sub Command1_click()
   Dim RVal As Long
   RVal = SendMessage(Combo1.hwnd, CB_SELECTSTRING, 0, ByVal soption1)
   If RVal > 0 Then
      RVal = SendMessage(Combo1.hwnd, CB_SHOWDROPDOWN, 1, 0&)
   End If
End Sub