Issue with custom report that shows all users registered for event in last 2 years but not this year
I have accomplished similar results to what you are looking for by doing the following.


I created a smart group for all those who have registered for the current event (2017)
I then used the participant report filters to include all registrants from the previous events (2015 &amp; 2016)
I then added a filter to exclude any members of the smart group for the current event.


I do all this using the report filters on the standard participant report but you could probably apply similar filters to a custom report. I also use the current event registrant smart group to exclude folks who have already registered from promotional mailings. It comes in handy.

Hope this helps.