Filter sales order in listpage salesorder num using modified method for stringedit Field in form

public boolean modified()
{
   boolean ret;

   ret = super();
  SalesTable_ds.queryBuildDataSource().clearRanges();
   if (this.valueStr() != '' )
   {
       SalesTable_ds.queryBuildDataSource().addRange(fieldNum(salestable, salesid)).value(this.valueStr());
       SalesTable_ds.executeQuery();
   }

   else
   {
       SalesTable_ds.queryBuildDataSource().addRange(fieldNum(salestable, RecId)).value("0");
       SalesTable_ds.executeQuery();
   }

   return ret;
}