how to remove event handlers by style?

hi.

i want to remove this event handler:

<Style TargetType="ContextMenu" x:Key="treeItemContextMenuStyle" ><EventSetter Event="ContextMenu.Loaded"  Handler="mainContextMenu_Loaded"/></Style>

private void mainContextMenu_Loaded(object sender, EventArgs e)
        {
            ContextMenu mainContextMenu = (ContextMenu)sender;

            mainContextMenu.Loaded -= mainContextMenu_Loaded;
            //this code not work for remove event handler
        }