Is there a way to do this : #import History module from OFS import History #derive from Historical mixin class Document(PortalContent, DefaultDublinCoreImpl, History.Historical): #add the History tab to the Zope Management Interface manage_options=PortalContent.manage_options+History.Historical.manage_op tions #override the manage_historyCompare method #NOTE: in this example I set the resultso f hte comparison into the REQUEST variable, historyComparisonResults #which is then rendered by a pagetemplate history_comparison def manage_historyCompare(self, rev1, rev2, REQUEST, historyComparisonResults=''): historyComparisonResults=History.html_diff( rev1.CookedBody(), rev2.CookedBody() ) self.REQUEST.set('historyComparisonResults', historyComparisonResults) return self.history_comparison(self.REQUEST) with DTML only ?