internal void PopulateCboLayers(object item)
        {
            map = (ArcMap.Application.Document as IMxDocument).FocusMap;
            CboFields.ClearAllItems();
            CboLayers.ClearAllItems();
            ILayer layer;

            for (int i = 0; i < map.LayerCount; i++)
            {
                layer = map.Layer[i];
                if (map.Layer[i] is IFeatureLayer)
                {
                    CboLayers.AddItem(layer.Name);
                }
            }
        }