Help using the INTERPOLATION-function

[Rune Svendsen <runesvend gmail com>]

Hi all!

I'm trying to figure out how to use the INTERPOLATION function, but I'm
not quite sure how to use it.
I've been reading up on using functions, but I get an error saying
"Invalid expression" when I try to use this function.

I do the following:

        1. Enter some data in A1 to A3 (eg. 1, 2, 3) and in B1 to B3
        (eg. 2, 4, 6)
        
        2. In A4 I enter: 4
        
        3. I enter the following expression in B4:
        =INTERPOLATION(A1:A3,B1:B3,A4)
        
What I'm trying to do is interpolate for the X-value in A4, using the
three X-values in A1, A2, A3 and three Y-values in B1, B2, B3, and
placing the result in B4. What am I doing wrong?

Thanks!

/Rune