[Radiant] any way to dynamically populate <r:random>?

[john muhl]

I'd like to insert part of a random subpage into the sidebar and  
figured it'd be a good fit for the <r:random> tag but so far am having  
very little luck. I've tried:

<r:random>
   <r:children:each>
     <r:option><r:title/></r:option>
   </r:children:each>
</r:random>

and even:

<r:random>
   <r:find url="/this/url">
     <r:children:each>
       <r:option><r:title/></r:option>
     </r:children:each>
   </r:find>
</r:random>

but they both just return the title of the parent page. Am I missing  
something simple or expecting the impossible. Does anyone have any  
suggestion how to randomly grab a page part from a dynamically  
generated list of pages, besides using javascript?

thanks