Reply To: Can GREP reference position on a page?

Short answer: No.

GREP is not magic, it's a simple text pattern matching system. And it uses a pretty narrow definition of 'text' as well — it's not aware, for example, of InDesign's line endings inside a paragraph, and so stuff like “pages” or “text frames” are totally out of its scope.

For something this complicated and specific you could look into TeX, it might be possible after a couple of years of intensive studying.