Treeview navigation problem

[Inhumanoid]

I want to navigate through a treeview with the keyboard while the focus is on another control (a textbox)..
When I hit vbkeyup I want to goup an item
when I hit vbkeydown I want to go down an item... I thought of the following code:

Private Sub Text1_KeyDown(KeyCode As Integer, Shift As Integer)

On Error GoTo EOF_Error

Select Case KeyCode
    Case vbKeyDelete
        m_bEditFromCode = True
    Case vbKeyBack
        m_bEditFromCode = True
    Case vbKeyUp
    '   tvwTree.SetFocus
        tvwTree.SelectedItem.Previous.Selected = True
    Case vbKeyDown
    '   tvwTree.SetFocus
        tvwTree.SelectedItem.Next.Selected = True
    End Select
EOF_Error:
    If Err.Number = 91 Then Resume Next
End Sub

This does not work completely because it will never exit the root node... It will only go up or down within the same path

How can I accomplish to make it go up an item when I hit vbkeyup and down an item when I click vbeydown ??