How do I identify multiple records within another module in a custom field?

How do I identify multiple records within another module in a custom field?

I'm trying to achieve the following setup:

1. Have a custom module named "Training Events"
2. Have a custom field within my new "Training Events" module which I can store the id's of "Contacts".
3. On the date of the event, I'd like to generate a report of all attendees

What would be the best way to do this with Zoho? 

I'm also using the Zoho API to achieve this. 

Thanks