It is possible to make custom reports with InfoMaker that include drill downs. See the chapter 5 of the Template Design Guide Using InfoMaker here:
http://www.cisco.com/en/US/docs/voice_ip_comm/cust_contact/contact_center/enterprise_reporting/reporting7_0/user/guide/wipce70d.pdf It is not possible to create new drilldowns directly from WebView however several existing standard reports have built in drill downs.