动态改变表单元素的fieldLabel文字

表单元素（id必须定义）

            var txtState = new Ext.form.ComboBox({
                fieldLabel: '起运国',
                id:'txtState',
                resizable: true,
                mode: 'local',
                store: STATENAMEstore,
                displayField: 'STATENAME',
                valueField: 'STATENAME',
                anchor: '50%',
                triggerAction: 'all',
                editable: false,
                forceSelection: true,
                maxLength: 50
            });

动态改变fieldLabel

Ext.getCmp('txtState').el.dom.parentNode.parentNode.parentNode.firstChild.innerHTML = '出口国家：';