Help with scheduling classes

Some time ago, I got some advice that helped me set up the first tab in this sheet.
Using the REF tab, and some arcane lookup wizardry, I was able to get the suggested implementation in place for the tab labelled Mon, wherein we could use a dropdown to select an unassigned class participant (who then disappears from the 'Unselected' column)

This was working, but when I tried to implement the other days of the week, I ran into trouble and got lost and abandoned the project.

Now I'm looking at setting it up again, this on a set of tabs like the one labelled newversionMon, one for each day of the week.
I've forgotten everything I learned about the first attempt, but am also wondering if there is an easier or more elegant solution for this.
I would like to use the same selection/unassigned thing happen for the staff as well. The Activity space will also be a dropdown populatied from the 'Activity Pool' on the page, but those are items I'm not worried about duplicating, so I could populate the dropdown from the actual Activity Pool itself.

Can anyone help?

We are a small non-profit serving a disenfranchised community, and I appreciate any advice.

Here's my best guess on what you're looking for.

I've used a similar approach to the one you had, albeit with more up to date Excel formulas.

A table on the Ref sheet with list of participant names then a column for Mon-Fri AM & PM that counts how many times the names appear in the AM/PM section of each day's sheet.
1 = it appears and is therefore excluded from the relevant column to the right of the table on Ref. 0 = doesn't appear and therefore shows in the relevant column.

Those columns are then used for data validation lists, utilising the # functionality to make them dynamic.

I've set it up for all days on both AM and PM for the participant names.

Hopefully easy enough to follow, so give it a try with the staff names. Feel free to shout for help if you get stuck and need more assistance.

BSB

Thanks. The dropdowns in the Participants section aren't populated with the list of available candidates, did you enter the couple that are there manually?
I'm wondering if I have an older version of Excel or something. If not, I'll go ahead and use these to set up those dropdowns and display the unassigned participants down below.

Thanks, I'll work on implementing the staff list as well as adding another display section, for people who are absent.

Tim

I entered them using the data validation rather than manually so it should all work if you're using Office 365.

I only applied the data validation to columns B, G, L and Q tho.

BSB.

It looks like I'm on Office Professional Plus 2019, I'll see about getting upgraded to 365. Or use my home account.

Thanks.

I've set up a Ref2 tab for the Staff validation and made some modifications to Mon tab that I'll have to replicate across the rest of the days.