Automate residency scheduling

I am looking to find a solution (excel or other) to help create rotation schedules for almost 45 residents (medical trainees) in our program. currently, this is done manually, to factor in various requirements of training over a number of blocks (usually 12-13), with each block being 4 weeks, and also factoring in leaves or trainees that are off cycle in their training. There are a number of mandatory and optional rotations/elective with mins/maximums of trainees per rotation. There are some softwares available online to do this, but looking to create some efficiency to the manual process.