How do I get a list of outputs in a single cell in Excel without a really long code?

I am trying to list all weeks in which a certain class is offered. We have workshops up to five days a week and up to five times slots per day. We review the schedule for these workshops biannually and I would like easily to be able to reference what weeks we are offering the courses when we rework the schedule.

Rough layout of our sheet

Generally I would like to list the workshops and then in the cell next to each one put "Week 1, 3, 5" for example. So this function would look at the range of cells for a week, determine if that workshop is included in them, and then proceed to list that week number (as listed in the upper left hand corner in this case cell A99).