i think the trick will be to use your report page footer. You will put in your lines there since it is normally 0 height. Count the number of matching records when you open the report (so you'll know how tall to make it on the last page) and keep a running total in the report's details. Once you are on the last record, set the report page footer and your vertical line's height based on the number lines you have for that (last) page.
The fun part is counting it all. Got kinda busy so i can't do it at the moment, but if i get some time a little later i'll see what i can whip up.
yikes !!!