private void newPage(string label, TreeView treeView){
HBox hbox = new HBox ();
hbox.Add (new Label (label));
Button button = new Button (new Image (Stock.Cancel, IconSize.Button));
hbox.Add( button );
hbox.ShowAll ();
myNotebook.AppendPage ( treeView, hbox );
button.Clicked += delegate {
treeView.Destroy ();
};
}