In-Portal has kApplication::LinkVar and kApplication::GetLinkedVar methods that allows to pass url parameter from one page to another via storing it in session.
So basically LinkVar looks in url for a given parameter and if not found then retrieves it from session. But, when parameter is found, then it stores it to session for further use.
Tags, I'm proposing to add will only call that kApplication class method I've mentioned.
Ready for testing.