Smooth XY Scatter

[km1184]

I'm trying to find an easy way to find a Y value for a given X value on a smooth line XY scatter chart. I want to find the values in between my data points. (i.e. I have data points for an X of 10 and 15, but not for 12). I understand that the smooth line is not a trend line. I tried all the trend lines and none seem to fit the chart accurately. Please help.

I'm new to the forum thing. Here's my email address:kmcgarvey@evanseng.com