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_options
 
#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 ?