Hi,
my suggestion for solution is to instead use the built-in functions that are available when creating header/footer.

There you find symbols which represent current page and also total pages. With the help of those, you can easily create a footer that looks like this on page 1: Page 1 (of 7) and that will look like this on the last page: Page 7 (of 7)

That also gives you the advantage of page numbers on each page.

Kind regards
Bjorn