It seems there is no way to do that, so I've solved this issue using a different approach: I added a properties file that is read by my listener (which extends ScheduledEventMessageComposer) to set the number of minutes between each execution and I set the trigger every minute. if the number of minutes is not correct, the trigger is just ignored.
Pablo, I believe you're right on both counts. Nice work!
If you wanted to even take it another step further, you could have your listener get the values from an MBean. That'd allow the someone to change the MBean settings in jmx-console, and then restart your listener - the period could be reconfigured without even a server stop/start. Also, if you want to see that functionality in the ESB, feel free to log a JIRA on it, I think that's something that would help others as well.