Create Yii Customized Form With Validator

I have some form, with css defined and with some textfields, let’s use the following as example

<link rel="stylesheet" type="text/css" href="test.css"/>

<form action="/em/call" class="myStyle">

field1:<input text="hello"></input>

<input value="submit" type="submit"/>


Is it possible to show validation error if field1 is non-empty using Yii built-in validator, if yes, how should I do that?

(In the example given by Yii, it seems using CWidget::form, i am not sure how to customized that in my project, where GUI has been defined)