If you want a field to appear only once for a group of records, it can't be in the detail section for any group. It would have to be either in a page header or section header. The first would be impractical as you'd need a new page for each group.
Must confess I'm wondering why you need a descriptor for fields as opposed to making the label descriptive, or why you'd repeat the same info across a page:
Field20 field20 Field20 Field20 Field20
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.