Ext NumberField 监听事件

Extjs NumberField 有两个文本框，当输完第一个文本框内容点击回车后，第二个文本框显示和第一个文本框内容*0.0003，该如何实现？我做了一个监听事件，第二个输入框不显示显示值。希望各位高手帮忙。var txthtje=new Ext.form.NumberField({fieldLabel:"合同金额",name:"htje",anchor:"90%",allowBlank:false});
var txtyzsfJe=new Ext.form.NumberField({fieldLabel:"应缴印花税",name:"yzsfJe",anchor:"90%",allowBlank:false,readOnly:true,blankText:"根据合同金额自动计算，不需要输入！"});
 var formwh = new Ext.form.FormPanel({
          labelAlign:"right",
            Align:"center",
            buttonAlign: "center",
            frame:true,
            bodyStyle:"padding:10px",
            method:"post",
            monitorValid:true,
            items:[{
              xtype:"fieldset",
              title: "应缴印花税",
              autoHeight:true,
              items:[
                {layout:"column",
                items:[
                       {columnWidth:.5,layout:"form",items:[txthtje]},
                       {columnWidth:.5,layout:"form",items:[txtyzsfJe]}
                }
              ]
            }],
txthtje.addListener(
{
specialKey:function (field,e){
if (e.getKey() == Ext.EventObject.ENTER){
htjechange();   
}
},
change:function (field,newValue,oldValue){
htjechange();
}
});
function htjechange(){
txtyzsfJe.setRawValue(txthtje.getValue*0.0003);
};
执行之后输完第一个输入框回车后，第二个输入框显示“NaN”，把“*0.0003”去掉，输完第一个输入框回车后，第二个输入框显示“function() {        return this.fixPrecision(this.parseValue(Ext.form.NumberField.superclass.getValue.call(this)));    }”，为什么会这样，我是新手，刚用ext不久，望高手不吝赐教！