[Zope] Fragmented DTML

Hi all, Would it at all be possible that one were to fragment dtml code between objects? Say you always use a header and footer, could you not enforce a <dtml-let data="SESSION.getSessionData()"> </dtml-let>between the header and footer? My thought is not as the developer is the only one that knows the header and footer are always executed in a chain. Just thought maybe someone thought of it before and had some kind of product or a suggestion how to enforce the CoreSession presence without rewriting everypage to make the data param. Thanks, Paz