Private Sub ListView1_DblClick()
  Dim lvhti As LVHITTESTINFO
  Dim dwState As LVItemStates
  Dim iIndent As Long
  
  ' If a left button double-click... (change to suit)
  If (GetKeyState(vbKeyLButton) And &H8000) Then
  
    ' Get the left clicked item
    Call GetCursorPos(lvhti.pt)
    Call ScreenToClient(m_hwndLV, lvhti.pt)
    Call ListView_HitTest(m_hwndLV, lvhti)  ' also returns iItem
    
    ' If the item's icon or label is double clicked...
    If (lvhti.flags And (LVHT_ONITEMICON Or LVHT_ONITEMLABEL)) Then
    
      ' Get the left clicked item's indent and state values
      dwState = Listview_GetItemStateEx(m_hwndLV, lvhti.iItem, iIndent)
      
      ' If the item is collaped, expanded it, otherwise collapse it
      If (dwState = lvisCollapsed) Then
        Call AddChildItems(lvhti.iItem, iIndent,  10 )
      Else
        Call RemoveChildItems(lvhti.iItem, iIndent)
      End If
    
    End If   ' ListView_HitTest
  End If   ' (Button = vbLeftButton)
  
End Sub