se me ocurre que hagas esto:
modo de VB
ListBox.Selected(ListBox.ListCount - 1) = True
con eso selecionaras la ultimo que metiste al listbox, si nolo quieres pones:
ListBox.Selected(ListBox.ListCount - 1) = True
ListBox.Selected(ListBox.ListCount - 1) = False
Modo Windows api:
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Private Const WM_VSCROLL = &H115
Private Const SB_BOTTOM = 7
y solo envias el mensaje al handle del listbox
Call SendMessage(ListBox.hWnd, WM_VSCROLL, SB_BOTTOM, 0&)