I am working on a little widget that shows the events a person has attended. An event typically has two stages, a pre-registration and an attendance. If a person pre-registers for an event but does not attend, they take a spot for someone that would've loved to go, so we want to discourage.
We want to visually show when a person has pre-registered but not attended.
The idea I have in mind is an icon with two puzzle pieces. The top piece becomes highlighted when a person has pre-registered. The bottom piece becomes highlighted after the person has attended. A complete puzzle means you have completed all your task.
I am not convinced this will be intuitive enough and I'm wondering if you have any suggestions to accomplish this task.