How to add error handling on dynamic binding list?

Hi, With spring 3.0.5 and jsp, I have created a jsp form that can handle nested list.
But I don't know how to create error handling for each element of the list that user entered.

Here is my jsp file:

<c:forEach var="article" items="${productbean.articles}" varStatus="loopStatus" >
                    <tr>
                       <td>Article Header</td>
                       <td>
                            <spring:bind path = "productbean.articles[${loopStatus.index}].header">
                                 <Error messages></Error>
                                 <form:input name = "header" id = "header" path="${productbean.articles[loopStatus.index].header}" size="85" 
                                             value="${article.header}"/>
                            </spring:bind>
                       </td>
                    </tr>
                    <tr>
                       <td>Article Description</td>
                       <td>
                            <spring:bind path = "productbean.articles[${loopStatus.index}].productDesc">
                                 <Error messages></Error>
                                 <form:textarea name = "productDesc" id = "productDesc" 
                                                path="${productbean.articles[loopStatus.index].productDesc}" 
                                                value="${article.productDesc} " rows="8" cols="65"/>
                            </spring:bind>
                       </td>
                    </tr>
                    <c:forEach var="pf" items="${productbean.articles[loopStatus.index].pointForms}" varStatus="loop" >
                        <tr>
                           <td>Article Point-form</td>
                           <td>
                               <spring:bind path = "productbean.articles[${loopStatus.index}].pointForms[${loop.index}].pointFormDesc">
                                     <Error messages></Error>
                                     <form:input name = "pointForm" id = "pointForm" 
                                                 path="${productbean.articles[loopStatus.index].pointForms[loop.index].pointFormDesc}" 
                                                 value="${pf.pointFormDesc}" size="85" />
                                </spring:bind>
                                <td>
                                    <a href="javascript:delete_pointform('${productbean.productId}', '${productbean.articles[loopStatus.index].articleId}', '${pf.pointFormId}')" ><img src="<c:url value="/resources/images/delete.jpg" />" border="0"></a>
                                </td>
                           </td>
                        </tr>
                    </c:forEach>

How to "bind" error to each element in a list?
Any pointers / suggestion is very much appreciated.
Thanks
Sam