Determine the number of filtered columns in GridView

Dear support,

I need a textlabel above the grid that displays the number of filtered columns.

My columnfilters are all implemented the way that is described in der following article http://docs.telerik.com/devtools/wpf/controls/radgridview/filtering/custom-filtering-controls.

Is there a property which contains the number of active filter that I can bind to my textlabel? Or how can I implement it to achieve this aim.

Thanks in advance

Marcus