property Items.SelectedItem ([Index as Long]) as HITEM

Retrieves the selected item's handle given its index in selected items collection.

TypeDescription
Index as Long Identifies the index of the selected item into the selected items collection.
HITEM A long expression that indicates the handle of the selected item.

If the control support multiple selection, you can use the SelectCount property to find out how many items are selected in the control. 

The following sample shows hot to print the caption for the selected cell: Debug.Print Group.Items.CellCaption(Group.Items.SelectedItem(0), 0).  

The following sample underlines the selected item in the first group:

Private Sub ExplorerTree1_SelectionChanged(ByVal Group As EXPLORERTREELibCtl.IGroup)
    If (Group.Index = 0) Then
        With Group.Items
            If Not hOldItem = 0 Then
                .ItemUnderline(hOldItem) = False
            End If
            hOldItem = .SelectedItem()
            .ItemUnderline(hOldItem) = True
        End With
    End If
End Sub