You didn't tell me where in your macro to "just add a line" so I tried
putting in various places but, each time, I got a compile error when
running the macro.

I then split my spreadsheet into 10 smaller spreadsheets (each with
50,000 rows) and used Excel's Subtotal command (in the Outline group
on the Data tab). I started it on the first spreadsheet at 2 PM.
Immediatly after each spreadsheet was subtotaled, I started the next
one. By 1 AM, 9 of the spreadsheets had been subtotaled. I then
started the subtotal process on the last spreadsheet and went to bed.
I guess it finished about 2:30 AM. It took about 12 1/2 hours to get
subtotals on all the spreadsheets!!!!!