Where to find TreeListViews ColumnHeaderClick Event?

Question

I'm developing a tool which shows data from a database in a hierarchical manner. As there are additional data for each item I'm using a TreeListView control to display them in additional columns. The number of columns is determined by user input.

The custom control that I'm using is Ricciolos TreeListView: http://windowsclient.net/blogs/ricciolocristian/archive/2008/03/22/a-complete-wpf-treelistview-control.aspx

My problem now is, that I need to catch the ColumnHeaderClick event to apply a sorting logic. I already interviewed auntie Google, but no results. Maybe somene here knows where to find such an event and how to determine which column header has been clicked.

Thanks