Graphics of two years..

I have three columns of data.

One with year (2007 or 2008), one with month (jan - dec) and one with a number.

How should I proceed if I would like a graphic showing the months (jan - dec) on x-axis and revenue on y-axis and two lines/series in the graphic (2007 and 2008), i.e. comapring 2007 and 2008 over a similar 12-month period?

To date I've only managed to get the graphics at best in one line with all the 24 months (jan 2007 - dec 2008) across one series/line.

Please help!