Have a look at the list:
http://www.reddotcmsblog.com/reddot-cms-render-tags-the-ultimate-list
maybe try something like
<reddot:cms>
<if>
<query
valuea="Context:CurrentPage.Elements.GetElement(opt_Type).GetHtml().IndexOf()"
operator=">" valueb="Int:0">
<htmltext>
<li><a href="<%!! Context:CurrentIndex.GetUrl() !!%>"><%!!
Context:CurrentIndex.Headline !!%></a></li>
</htmltext>
</query>
</if>
</reddot:cms>
above example is untested, have a look at the list, if you're familiar
with .net/javascript you might make some sense of it :)