Java Filter class for Search to customize

Hi,

My required is after submission of stand search screen, I have to update my search query based on user inputs for one of the attribute.  what's the filter class & service to use for search before pull the service

            String idcService = binder.getLocal("IdcService");

            if (idcService != null & idcService.equals("GET_SEARCH_RESULTS"))

                  {

                          //custom condition before setting the value for xCustAttribute

                        binder.putLocal("xCustAttribute","XXXX");

                        return CONTINUE;

                    }else