Step Chart Approach 1: XY Chart with Error Bars

One way to get horizontal and vertical lines from data points is with error bars. You don't need to add points to get the additional segments. However, you do need to add formulas to compute custom error bar values, and you need to assign error bars to the series. Because horizontal (X) error bars are needed, the chart must be an XY chart with its inferior date scale axis, not a Line chart.

Step Chart Approach 2: Line Chart with Repeated Ranges

Until recently I considered only two techniques for building step charts: the XY plus error bars approach described above, and manually (i.e., tediously) inserting extra data into the worksheet to allow for one point per corner. But in February 2006, Michel Gerday of Belgium described the following technique in the Microsoft Excel Charting newsgroup, and his technique automatically adds the extra data to a line chart.