[Zope] dtml radio button

[Jianping Zhu]

in the form file i have:

<form method="post" action="actCreateUser">

<table cellspacing="2" width="100%">
	<tr>
	<td ><em>Are you using this book to teach?</em></td>
            <td ><input type=radio name=teach value=y>Yes</td>
	    <td ><input type=radio name=teach value=n>No</td>
	 </tr>
							     
</table>
</form>

in file acCreateUser, I want to do that if use choos Yes radio button, i
will set varible t to string Yes otehrwise set t to string No .
I have:
       <dtml-if "teach=='y'">
       <dtml-let t="Yes"></dtml-let>
       <dtml-else>
       <dtml-let t="No"></dtml-let>
       </dtml-if>
But this does not work i get error "name 'Yes' is not defined". how can
i fix this problem?

Thanks