FB "groups" how to generate a pop up msg *every* time a new topic is posted

Hi folks.
Re a Facebook gardening group that has worldwide members.
I wish that whenever a *new* topic is created, *before* the topic goes live, for the poster to see a pop up asking (in this case) "Have you remembered Rule 5 and told us where in the world you live"
Any thoughts on how to achieve this would be gratefully received as all the Admins spend SO long manually attending to this !!
Regards to all
John B in the UK WordPress ...