I understand your reluctance. Any solution I can imagine is going to involve IF fields testing for whether you are on an even page or an odd page and creating two text boxes, one for even and one for odd. That would respond to changes in pagination but would be a real pain to set up. Once you have it set, though, you could save this field as an AutoText entry. You would still need to put in the page numbers.

This may help: Microsoft Word Field Maths Tutorial