If you have a template, there is no need to have buttons on the ribbon to define the page numbering. All of that should be defined in the template itself. From your description, the template needs three Sections, each delimited by a "Next Page" Section break:
1. Front matter; page #s formatted as Roman Numerals, in X of Y format.
2. Body; page #s formatted as Arabic, in X of Y format
3. Appendices; no page #s.
Configured that way, the 'Y' expressions for both numbered Sections can be calculated via SECTIONPAGES field.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]