EXTJS 资料 combo 点一次触发一次

{
              xtype: 'combo',
              id: 'ApplyToModel',
              name: 'ApplyToModel',
              store: comStoreApplyToModel,
              valueField: "Id",
              displayField: "ChineseName", width: 150,
              mode: 'remote',//local
              editable: false,
              triggerAction: 'all',
              autoload: true,
              listeners: {
                  "expand": function (combo, store, index) {                     
                      comboData_DynaPropertyValue.load({
                          params: {
                              PropertyId:'' , //获取当前选择行的字段ID
                              start: startDynaProperty,
                              limit: limitDynaProperty
                          }
                      });
                  }
              }
          }