Search for NOT in a certain project

Hi, is there a way to search for all records of X in region Y except for those that were included by a city challenge? The round abound I am using is to download all the records and then exclude occurances recorded in this certain city, which is not exactly the same thing.
Thanks.
Gabriela

You can exclude a geography from your search, for example show me results from England but exclude London, there is also a not_in_project parameter you can apply to your search.

Not sure which is more tied to your search objective, do you want in my example to exclude all London, or only London from the CNC weekend for instance.