Hi,

Enter your benchmark figure in a cell. This will be your y value.
Add a suitable x value in the cell to the left of your y value.
Plot these as a new series and change the chart type to x-y. (You may need
to change it's axis back to primary.)
Add an x error bar extending to the right, format the error bar.
You can smarten it up by hiding the data point.
Add a data point to show the y value.

Let me know if you want an example. I use these all the time.

Dave

url:http://www.ureader.com/msg/10296039.aspx