[Zope] small <bobobase_modification_time> problem

Following Problem: I am using <bobobase_modification_time> in my standard_html_footer. It works fine if I am changing the index_html in which the standard_html_footer is included. But the index_html has also a variable "news"(dtml-method) included. If I am changing the news, the <bobobase_modification_time> doesn't change ;-(. So my Site changed, but not the modification time. Is there a way to solve this? thanks Damir