extJs 文本框后面加上说明文字+下拉列表选中值后触发事件

var showForm; 
function panelShowForm() 
{ 
showForm=null; 
showForm = new Ext.FormPanel({ 
renderTo:"showPanel", 
region:'north', 
border:false, 
bodyBorder:false, 
frame:true, 
waitMsgTarget: true, 
labelAlign:'right', 
id:"showForm", 
items:[{ 
layout:'column', 
labelWidth:129, 
items:[ 
{ 
columnWidth:.6, 
layout:'form', 
items:{ 
name:"enable", 
hiddenName:"enable", 
fieldLabel:'是否启用密码策略', 
xtype:'combo', 
editable: false,//不允许输入 lazyRender:true, 
blankText : '必须启用密码的侧咯', //为空默认值 
allowBlank : false, //不允许为空 
mode: 'local', 
triggerAction: 'all', 
store:new Ext.data.SimpleStore({ 
fields: ["value", "text"], data: [['1','启用'],['0','禁用']] 
}), 
// 这两项要与上面的fields对应 
valueField :"value", 
displayField: "text", 
listeners:{ change:function(){changeValue();} 
}, 
anchor:'100%' 
} 
},{ 
columnWidth:.4, 
layout:'form', 
items:{ 
hiddenName:"infoFillOne", 
name:"infoFillOne", 
xtype:'label', 
html:'<font color=red>设置为禁用,则以下面项不可用</font>', 
labelSeparator:'', 
anchor:'100%' 
} 
},{ 
columnWidth:.6, 
layout:'form', 
items:{hiddenName:"updateDay", 
name:"updateDay", 
xtype:'textfield', 
fieldLabel:'更新周期', 
emptyText : '设为-1该项被禁用', 
maxLength:'100', 
readOnly:false, 
vtype:'day', 
anchor:'100%' 
} 
},{ 
columnWidth:.4, 
layout:'form', 
items:{ 
hiddenName:"info", 
name:"info", 
xtype:'label', 
//labelAlign:'left', 
html: 
'<font color=red>设置为-1,则该项被禁用</font>', 
labelSeparator:'', 
anchor:'100%' 
} 
}] 
}] 
}) 
} /** 
*是否启用密码的触发事件 
*/ 
function changeValue() 
{ 
if(queryForm.form.findField('enable').getValue()=="0") 
{ 
$("updateDay").disabled = true; 
}else{ 
$("updateDay").disabled = false; 
} 
} 
/** 
*窗口的显示 
*/ 
function input() 
{ 
panelShowForm(); 
win=new Ext.Window({ 
title:"extJs 文本框后加上说明文", 
width:200, //窗口初始width值 
hight:200, //窗口初始hight值 
x:100, //窗口初始的x位置 
y:100, //窗口初始的y位置 
plain : true, 
modal : true, //模式窗口 
maximizable:true,最大化显示 
resizable:false, //窗口的大小不允许拖动 
items:[showForm] 
}) 
}