I'm sure there are more elegant ways to get a horizontal bar in a report,
but, in design view, I used the line tool in the tool box and inserted
vertical lines in detail and header sections between the fields I wanted to
separate. I had to "play" a bit with the height, weight & color of the line
to get a result that didn't lood too stark, but I liked the end result.

Frank:

There is no real way to create vertical separators.  However, see if you can
either:

1.) Create a month value for your graph that has a 00 month.  (you could do
this if you create a table with 00-12 in it, separate the month from the
year as a field and use an outer join from the table to the query that has
the actual months in it.  This of course would create a bar with no value
but would you could fudge with the formatting to have it just display the
year.

2.) The Graph object itself does contain an option to set the spacing
between bars, but it changes the value for all bars rather than just one,
but you could play around with that to enhance the readability of the chart.

HTH