Random population of Excel matrix

I have 100 assignments to be reviewed and 23 reviewers. Each assignment must be reviewed by 3 separate reviewers. How can I randomly allocate the assignments to the reviewers such that each assignment is reviewed 3 times and each reviewer has an equal workload?

I do not want any subset of reviewers to review the same subset of assigments hence the requirement for random allocations.

I have heard that Excel can do this but can't figure it out myself.

Any suggestions?

Thanks

John