Help needed

Hi everyone, I'm new, I registered because I have hit the limit of my know how and after looking at all the various forums, this seemed the most responsive and knowledgeable.

I have a spreadsheet I am making tracks 2 aspects-

1 Tab/sheet for SLA's (chronological list of registrations with time stamps as they move through a physical process)

Then multiple tabs (each named after the event e.g sheet2 '15th June) for events they have either attended or are booked onto, the layout of the other tabs is different but will include their email address.

I want to create a cell (R) on the SLA tab that lists the individual tab/sheet names the email address appears on eg- 15th June, 22nd June, 26th June etc etc BUT if they are not registered on an event (therefore not on any of the other tabs) display 'No Activity'

I hope I have been as descriptive as needed and any help would be greatly received.

Thanks

Gareth