帮忙看看这个extjs的简单问题

Question

就是在下面填入选择题数目，以及后面设置好选择题的分值后，上面的试卷总分随着下面填入的数字改变而改变。
是不是要写个addListener? 应该怎么写啊   谢谢~！！！！
var top = new Ext.FormPanel({
        frame:true,
        bodyStyle:'padding:5px 5px 0',
        width: 440,
        height: 250,
        labelWidth:60,
        items: [
         layout:'column',
         items:[{
          columnWidth:.5,
                layout: 'form',
                items:[{
                    fieldLabel: '试卷总分',
                  xtype:'textfield',
                    allowBlank: false,
                    name: 'totalScore',
                    vtype:'number',
                    emptyText: '请指定试卷的总分', 
                    anchor:'95%'
                }]
         },{
          columnWidth:.5,
                layout: 'form',
                 items:[{
                    fieldLabel: '剩余分数',
                  xtype:'textfield',
                    name: 'lastScore',
                    readOnly:true,
                    anchor:'95%',
                    emptyText: '剩余的可分配总分'
                 }]
         }]
        }        ,{
            layout:'column',
            items:[{
                columnWidth:.33,
                layout: 'form',
                items: [{
                    xtype:'textfield',
                    fieldLabel: '选择题',
                    emptyText :'题数',
                    name: 'choiceNumber',
                    vtype:'number',
                    anchor:'95%'
                },{
                    xtype:'textfield',
                    fieldLabel: '判断题',
                      emptyText :'题数',
                    name: 'judgeNumber',
                     vtype:'number',
                    anchor:'95%'
                },{
                    xtype:'textfield',
                    fieldLabel: '主观题',
                     emptyText :'题数',
                    name: 'subNumber',
                     vtype:'number',
                    anchor:'95%'
                }]
            },{
                columnWidth:.33,
                layout: 'form',
                items: [{
                    xtype:'textfield',
                    fieldLabel: '现有选择',
                    name: 'choiceNow',
                    readOnly:true,
                    anchor:'95%'
                },{
                    xtype:'textfield',
                    fieldLabel: '现有判断',
                    name: 'judgeNow',
                     readOnly:true,
                    anchor:'95%'
                },{
                    xtype:'textfield',
                    fieldLabel: '现有主观',
                    name: 'subNow',
                      readOnly:true,
                    anchor:'95%'
                }]
            }
            ,{
              columnWidth:.34,
                layout: 'form',
                items: [{
                    xtype:'textfield',
                    fieldLabel: '设定分值',
                    name: 'choiceScore',
                    vtype:'number',
                    anchor:'95%'
                },{
                    xtype:'textfield',
                    fieldLabel: '设定分值',
                    name: 'judgeScore',
                    vtype:'number',
                    anchor:'95%'
                },{
                    xtype:'textfield',
                    fieldLabel: '设定分值',
                    name: 'subScore',
                    vtype:'number',
                    anchor:'95%'
                }]
            }
            ]
        }]
        });

Answer 1

是要写addlistener吧，绑定change事件。？ 等会写下试试。。

Answer 2

给每一个"设定分值"加listeners ： 
                   xtype:'textfield',
                    fieldLabel: '设定分值',
                    name: 'subScore',
                    vtype:'number',
                    anchor:'95%',
                    listeners : {
                        'keydown' : function(){
                            //计算和 然后给"总分"组件赋值
                         }
                    }addListeners是动态给组件加事件 适合动态生成的组件