Singe Time-Line Graph with Multiple series

I have a 2 column set of data, Year and Concentration. It is data for the years 1940 through 2000, and I want to plot it so that it is continuous single line series for the entire time period, but broken into 3 different colored segments for the years 1940 - 1990, 1991 - 1988, and then 1999-2000.

When i attempt to plot the data by just highlighting the segments of Concentration as individual series for the y-axis, and the entire Year column as the X-axis, all the data just overlaps. I did manage to figure that If i pull out the data so that each segment has its own column and the rest of the years in that column where there is no data for that segment series is left blank, it will plot it continuously.

However, I was wondering if there is an easier way to do this? Thank you.

I am operating on the latest Excel btw, no longer 2007 ha!

so change version in your profile, ha!