You have a choice, you can choose to:
1. Hard code the y value or
2. Put a bookmark on the last page of section 2 (ie. where you want the y to get its value from). Then in the footer you replace the y with a crossreference field pointing to that bookmark. The footer fields in sections one and two would then end up something like
Page {Page} of {PageRef BookmarkName}

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Andrew Lockton
Chrysalis Design, Melbourne Australia