How to make checkboxs required in a Spring WebFlow Project with Dojo. I would like to know how to make the checkbox required on submit of the following page. I don't want the submit to work if the user did not click one of the check box options. thanks.

Code:
  <%@ taglib prefix="c" uri="http://java.sun.com/jstl/core"%>
    <%@ taglib prefix="fmt" uri="http://java.sun.com/jstl/fmt"%>
    <%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>
    
    
    
    <style type="text/css" media="screen">
     @import url("<c:url value="/resources/dojo/resources/dojo.css"/>");
     @import url("<c:url value="/resources/dijit/themes/claro/claro.css"/>");
    </style>     
    
    <script djconfig="parseOnLoad: true"
     src="<c:url value="/resources/dojo/dojo.js"/>" type="text/javascript"></script>
    <script type="text/javascript"
     src="<c:url value="/resources/spring/Spring.js" />"> </script>
    <script type="text/javascript"
     src="<c:url value="/resources/spring/Spring-Dojo.js" />"></script>
    <script type="text/javascript">dojo.require("dojo.parser");</script>
    
    <html>
    <head>
    <title>Spring 3.0 MVC - Web Flow Example</title>
    </head>
    <body class="claro">
    	<h2>Dropdown Test</h2>
    	<p>
    	<p>
    	<form:form commandName="customer" id="customer">
    		<input type="hidden" name="_flowExecutionKey"
    			value="${flowExecutionKey}" />
    		<div id="container">
    			<table>
    				<tr>
    					<td><font color=red><form:errors path="sex" /></font><b>Sex:</b></td>
    					<td><form:checkbox path="sex" id="sex" value="MALE" /> Male - 
    					    <form:checkbox path="sex" id="sex" value="FEMALE" />FEMALE
    					    <script type="text/javascript">
    							dojo.query("#sex input[type='checkbox']").forEach(function(element){
    								Spring.addDecoration(new Spring.ElementDecoration({
    									elementId: element.id,
    									widgetType : "dijit.form.CheckBox",
    									widgetAttrs : { checked : element.checked, required : true }
    								}));
    							});
    						</script>
    						</td></tr>
    						</table>
    		</div>
    		<p>
    		<input type="submit" name="_eventId_submit" id="submit" value="Submit" />
    		<input type="submit" name="_eventId_cancel" value="Cancel" />
    		<p>
    		<script type="text/javascript">
    			Spring.addDecoration(new Spring.ValidateAllDecoration({
    				elementId : 'submit',
    				event : 'onclick'
    			}));
    		</script>
    	</form:form>
    </body>
    </html>