To determine when a field value changes, use Sorting and
Grouping (View menu) to specify the field. Also set it to
include a group header section.
Now, you can set the group header section Force New Page
property to Before Section to start a new page when the
value changes. The header section's Format event procedure
can then be used to (re)set the page number using a line of
VBA code:
Me.Page = 1