See (It allows execution of wiki code and parser functionshttp://www.mediawiki.org/wiki/Extension:ParserFunctionswithin tags before the tag is processed.)
{{#tag:*tagname* |*content* |*attribute1=value1* |*attribute2=value2* }}
on
http://www.mediawiki.org/wiki/Help:Magic_words#Miscellaneous
Daniel Forgues
mediawiki-l@lists.wikimedia.org