Schedule an ESS job to run for every X minutes between some Y and Z hours.

I am looking to schedule an ESS job to run for every 3 hours between 8am to 6pm daily.

i.e. Run times will be 8am, 11am, 2pm and 5pm every day for the whole year.

Currently we have Create Accounting job scheduled to run for Cash management once a day. But on some odd days if the bank statement arrives late, the schedule does not post these transactions on the same day. We don't want any business users manually running this job, so we want to setup custom timings to account for the late arrival of bank file.