How to autofill rows until manual change in Numbers

I created a form for studying that has a column for “Page Number”.

I want to type in an entry, e.g. “6” for page 6, but I also want every subsequent entry to essentially act as an “ibid” entry, automatically filling-in a “6” until I manually change it, say to “7”, and then it would continue auto-entering “7” until I’m ready to enter some other number and go on from there.

As you can in the image below, there are numbered entries for both “Chapter” and “Page No.” columns. I’d like the blank spaces to essentially repeat the entry number above them until such a time as a new entry number is entered.

[Re-Titled by Moderator]