How to update process variable from event handler

There is api to update process variable like: processApi.updateProcessDataInstance("x",processInstanceID, 100) but within isInterested(SEvent event) method of event handler i am not getting the reference of processApi. Within groovy script i can easily write like: apiAccessor.getProcessAPI().updateProcessDataInstance("x", processInstanceId, 100) but within event handler class i am not getting the reference of processApi. Bonita BPM version is 6.3.2 java version "1.6.0_23" tomcat & windows 7