listeners : {
       beforeload : function (store, options,eOpts) {
              var process = Ext.getCmp(store.rowId+"process").getValue();
              var new_params = { processNameParam: process  };
              Ext.apply( store.proxy.extraParams , new_params ) ;
       }
}

process 为获取前台的值,processNameParam 为传到后台后的值的变量。
如通过 struts 获取: private String processNameParam; (setter 和 getter-OGNL)
后台打印:

System.out.println(processNameParam);