Hi Sanjay,

Thank you for posting in our forums!

The ValueLabel can be customized in this case through the FormatValueLabel client side event.  Please see the code snippet below for the function I have used for this:

 function WebSlider1_FormatValueLabel(sender, eventArgs) {
     ///<summary>
     ///
     ///</summary>
     ///<param name="sender" type="Infragistics.Web.UI.WebSlider"></param>
     ///<param name="eventArgs" type="Infragistics.Web.UI.SliderFormatValueLabelEventArgs"></param>

     var value = eventArgs.get_value();
     if (value >= 12) {
         eventArgs.set_label("12+");
     }
 }
 

I have also attached my sample for you to examine in full.  If you have any further questions or concerns with this, please let me know.