I've been taught this phrase in another course but never really understood its use - ça y est. It was presented to me as one of those catchall phrases for "yes, that's right!", "yeah, that's it" as a somewhat utterance one makes to ones self (or to others) that you've been suddenly successful at something or an acknowledgment that you're at least on the right track. So I used this here instead of "c'est ça". Did I use it correctly? I actually had "c'est ça" first but then I changed it to see if I had actually finally found a way to use "ça y est" correctly.
(By the way, why can't I use the hold down the keyboard trick to apply accents, etc in this Q & A box? I have to admit it prevents me oftentimes from asking questions since I can't be precise.)