If I have some data in an scatter plot in Excel, e.g.

X Y
1 10
2 20
3 30
4 40
5 50

and I want to find the Y value for X = 10, or X=3.5, or whatever (obviously this is a simplified example) I've been doing the following:

• Add a trend-line to the scatter plot data
• Format the trend-line to one that fits the data (linear in this case)
• Display the equation for the trend-line on the chart
• Type the equation into an empty cell, replacing x with a cell reference. E.g. "=10*A1" then put my X value into the cell A1

Is there a better way of doing this with Excel? It's quite a few steps, and fairly repetitive. Or maybe Excel is just a poor choice of application for doing this?

(I'm using Excel 2007)