property Items.ItemHasChildren (Item as HITEM) as Boolean

Adds an expand button to left side of the item even if the item has no child items.

TypeDescription
Item as HITEM A long expression that indicates the item's handle.
Boolean A boolean expression that indicates whether the control adds an expand button to the left side of the item even if the item has no child items.

Use the ItemHasChildren property to build a virtual tree. Use the BeforeExpandItem event to add new child items before expanding a fake item. Use the ItemChild property to get the first child item. Use the ItemChild or ChildCount property to determine whether an item contains child items.  

Private Sub ExplorerTree1_BeforeExpandItem(ByVal Group As EXPLORERTREELibCtl.IGroup, ByVal Item As EXPLORERTREELibCtl.HITEM, Cancel As Variant)
    With Group.Items
        If (.ItemData(Item) = 1234) Then
            add (Item)
            .ItemData(Item) = 1111
        End If
    End With
End Sub