The GUI scheduler can be used in cron mode which provides more granularity than our standard schedules.
The GUI scheduler is quartz and the documentation can be found here: http://www.quartz-scheduler.org/docs/tutorials/crontrigger.html
An example of a schedule to run monday through friday between 8-17 would be as follows:
0 0 8-17 ? * MON-FRI
One trick is the ? which basically ignores field must be either set for month or day of week so either the 4th or 6th field. Also a minimum of 6th fields is required. The optional 7th field is documented in the above URL.
Regards,
Keith