In what movie does Ron Weasley reply to Hermione, both saying "the whole city" See full question in details. Thanks.

Harry Potter experts...please help if you can. The kids and I are having a debate over a line we think comes from a Harry Potter film, but we can't seem to find it. There is a scene, I don't know when or in which film, where Harry, Hermione, and Ron Weasley are talking about something - some risk or possible evil, and Hermione says something about it either affecting the whole city or that in order to accomplish their task they would need to do something in, or look in, the whole city. Ron replies in disbelief, and animatedely with quite the heavy English accent , "The whole city?!?!?" (and makes quote an animated face as well) and the city comes out in the heavy accent as if two words with a pause between the two, like "sit. eeh." Not making fun of anyone or anything, it just kinda stuck with us and we say "the whole city?!?!" a lot in real life situations, and now the kids swear it's from a Veggie Tales story about Ninevah, and the "guards" say it, but I swear it was from a scene in Harry Potter, and Ron Weasley said it in reply to Hermione. Naturally, my kids would love to prove their old man wrong, and I would love to know I haven't completely lost it yet (mid 40's), so anyone who might know this and can point me to which movie and roughly where it is in that movie, I would be eternally grateful. :-) Thanks in advance.