In fact you can see it as a cheap replacement of some DHTML.
The content of the page is displayed via a ditto call where the given template depends on whether you want a concise or detailled view. So the name of the template is simply built using a query string parameter read through a TV.
[!Ditto? ... &tpl=`eventList[*chunkDetailParam*]Chunk`!]
chunkDetailParam is the name of the variable that evaluate the param. The value of the variable is as follow :
@EVAL if (isset($_GET[’chunk’])) { return $_GET[’chunk’];} else { return ’’; }
lionel