Salmonh:
Yes you can have Excel chart the last 9, 30 or whatever number of values
that you would like.
You'll need to use dynamic range names to do this. Here are several links
that will get you started.
http://www.stfx.ca/people/bliengme/ExcelTips/Dynamic.htm
http://processtrends.com/pg_chart_tips.htm#Dynamic_Chart_Range_Names
http://peltiertech.com/Excel/Charts/Dynamics.html
The idea is to create dynamic ranges that will update as you add data and
will set the last 9 values as your plot range.
For a simple data set of X and Y in Cols A and B, you would use 4 offset
formulas:
First we set up a range name for the last data row
last_row =OFFSET(Sheet1!$A$1,COUNTA(Sheet1!$A:$A)-1,0)
Second: we set up a range name for the first data row that we want to plot,
using your 9 example:
first_row
=OFFSET(last_row,-8,0)
Third: we set up the dynamic X value range name using the first and last
rows:
dyn_x =OFFSET(first_row,0,0,last_row-first_row+1)
Fourth: we set up the dynamic Y value range as an offset to the dynamic_X
range
dyn_y =OFFSET(dyn_x,0,1)
We are now set to create our chart. I do this by creating my chart using the
chart wizard. When I have my chart formatted and set the way I want, I edit
the chart series formulas and replace the X value range with dyn_X and the Y
value range with the dyn_Y range name.
If you want another period besides 9, edit the offset formulas.
You also asked about interactive charts. There are many interactive
examples. If you give me an idea of the type of interaction you are looking
for, I can give you links to specific examples.
...Kelly
(e-mail address removed)