I think I've figured out a workaround - There is a heading line that starts the second section; if I put the section break after this heading line, then the # of pages in the first section would be the page number that I am looking for (the page which contains this header). Technically, it is part of the second section, but if it works properly then this may be the best solution.

Plus, the first section is 1 column, and the second section is 2 columns, and that would allow the header to span the columns, which is probably preferable as well.

Thanks again for your help, I know I wouldn't have gotten there without it!