Hi Yahya,

I have a chart in Excel 2007 and I want to provide a Y value (that is not
one
of the data points) and have Excel to tell me the corresponding X value
from
the chart. How can I do that?
The chart is not a straight line, so trendline won't work
Here is a picture of the chart I'm working on
http://hkoyda.blu.livefilestore.com/...x_wA/graph.JPG

Any help in this matter would be greatly appreciated.
Yahya

You can't do that without knowing the formula for your line of best fit.

There is a sample here
http://www.edferrero.com/ExcelCharts...2/Default.aspx called 'Reading
Interpolated Values' that works for a straight line. The sample uses
click-and-drag on the chart which will not work in Excel 2007. However, you
can manually change the x-Value at cell E4 to calculate the intercept at a
particular x-Value.

Looking at your picture, I would try calculating the log of the y-Values and
charting that. If this is close enough to a straight line for your purposes,
then just use my sample to calculate the intercept. =LN() to find the log,
=EXP() to change back.

Ed Ferrero
www.edferrero.com