Excel 2010 Charts - Line Graph - How to specify which line is on top?

Hello,
I have a line graph with three lines, there are 2 points that two of the lines have in commmon.
Right now, the green line shows these two points but I want the black line to be the one on top... how can I do this?

When I right click > Select Data Source > I can move the Series up or down, but this just changes the order of the legend, not the layering of the lines... any ideas?

Thanks