Hi Darren, if they downloaded the report previously, are they already members of a certain campaign? Or were they already sent a specific thank you email? You can utilize something along those lines to filter someone out, an example would be:
Member of program: Your Webinar, Program Status is Attended
AND
Not member of program: Your report download program
or you could do
Member of program: Your Webinar, Program Status is Attended
AND
Not sent email: Thank you for downloading your report