Vertical lines on a chart?

I am creating a forecasting report with a basic line graph (chart) and I am having trouble figuring out how to put in a vertical line in my line graph. I have a 52 week chart and would like to show separation for the different seasons of the year. So what I want is a vertical line on weeks 13, 26, and 39. I tried to add another legend series at each of those points (13, 26, 39), but when I do that it comes out as a triangle, which makes sense. Any other ideas on how I could accomplish this? Thanks for any help and ideas!
-Ryan

I figured one way to do it. It takes some time to accomplish it, but it works.
http://www.exceldashboardtemplates.c...el-line-chart/