Dynamic Step Chart using range names
(Rev 1)

Let's create a step chart to illustrate Fed Funds Rates
Data at http://www.federalreserve.gov/fomc/fundsrate.htm

I create a new book and save it as "Step.xls" (a short name is good idea...
see at III)

| A B
--|----------- ----
1| Date Fed
2|03-Jan-2000 5.50
3|02-Feb-2000 5.75
4|21-Mar-2000 6.00
5|16-May-2000 6.50
6|03-Jan-2001 6.00
7|31-Jan-2001 5.50
8|15-Feb-2001 5.50
9|

II. I have to define Range Names with Insert,Name,Define...

1. NbDate =COUNT(Sheet1!$A:$A)
= I count the number of cells in that contain numbers

2. Date: =OFFSET(Sheet1!$A$2,0,0,NbDate,1)
= I start from cell A2 because A1 contain the label
= I subtract 1 because label in cell A1 was counted

3. DateX: =OFFSET(Sheet1!$A$2,1,0,NbDate - 1,1)
= I want the same range of dates except the first date

4. Fed: =OFFSET(Sheet1!$B$2,0,0,NbDate,1)
= Same as for Date

5. FedX: =OFFSET(Sheet1!$B$2,0,0,NbDate - 1,1)
= I want the same range of Fed values except the last one

6. FedLabel: =Sheet1!$B$1 (not mandatory)

III. I have to create the chart

Insert,Chart...,Line,Line chart without marker,Next
Select the "Series" tab
Click on "Add" series
- Name: =Step.xls!FedLabel (Spreadsheet name is mandatory!)
- Values: =(Step.xls!FedX,Step.xls!Fed) (Union of 2 ranges !)
- (X) axis: =(Step.xls!DateX,Step.xls!Date)
= the comma is the character defined as "List separator"
in the Windows Regional and Language Options.

Click on Finish... That's it !

IV. When the Fed changes its rates, feel free to add a row of
data to see the chart change dynamically...

===
Notes:
1. This works because Excel recognised the Date ranges as a Time Scale X
axis (as mentioned early by Andy Pope at http://www.andypope.info).
2. It also works with a "number" X axis with x 0
3. Done with Excel 2002.
4. Rev 1: use of NbDate, COUNT instead of COUNTA, full spreadsheet name.

Post Scriptum: Thanks Jon for your comments.