Based on the DS Mapbook - Detailed Area Insets toolbar (developed out of the Denver regional office) for ArcGIS 8.X, this data-driven pages version will auto-build insets in the layout at a more zoomed-in scale from the main data frame. Insets are auto-generated by referencing an index feature class at a specified, more detailed scale. This is perfect for utility system mapbooks that need to show connections, etc. This is fitting...until engineers and public works crews move fully to digital, dynamic maps.