Study Normalization and Relationships before you proceed to build an Access database.
You have a many-to-many relationship: an Event can have many participants and one participant can go to many events. NO relational database management system, like Access, likes this situation. So, to resolve this, you will create a "junction table" to create two one-to-many's.
You will have three tables: tblEvents, tblPart., tblAttend.
The tblAttend will look like this:
AttendID Primary key
EventID Primary key of tblEvent
PartID Primary key of tblPart.
DateAttended Any COMMON fields to both Event and Particip.
Then in query, you will connect tblEvent to tblAttend through EventID AND tblPart. to tblAttend through PartID. This creates two one-to-many's and retreiving info is now quite easy.
Warning: if you don't study or take courses in Access, you'll have major problems down the road.