Spline Interpolation in Excel

I'll make this clear and simple, since I'm on a deadline here. Doing some reports for my section, and I came to a part where I could really use an interpolation in Excel.

Now, I've never had any practice with its functions, or VBA in general. So, is there a place where I could, or do anyone of you guys know some, ... where I could pick up a simple spline interpolation along with a tutorial of "how to make it work" (literally, I have no idea - I use Excel on a one-handful-of-times-on-an-annual-basis)?

I just need something that will put up a spline (or something similar) on an x and y column of values, and give me the interpolated result given values of X.

p.s. I know however of trendlines, but they're no use for me in this case. I cannot get the coefficients "programmatically" ...

I'd really appreciate some pragmatical help.