This chart displays a line that changes colour depending on whether it is above or below a control line. It is based on a xy-scatter chart.

The formula calculates all the intersections and then the sorted values are plotted using 2 series.

Full credit goes to Dave Curtis, a forum member at OzGrid. who provided the formula to calculate the intersections.

I was able to add the formula to dynamically sort the resulting values.

Update 16th February 2008:
Apollo Huang, a fellow MVP from China, pointed out a flaw in my sorting formula, which was picking up incorrect cell values. I have incorporated his formula revision in to the download.

The download contains data based on the RAND function so will generate new values automatically.