help with interpolation and limit of interpolation
 

2 questions for the ng

1) I've got 2 series of values in column A and B. I use a function to
interpolate the series for a certain value in C1 (that refers to data in
column B)

cspline_interp(A1:A100;B1:B100;C1)

now, how can I define the interval of interpolation as A1:"Amax" ? In other
terms, I just want to limit the interpolation to values between A1 and
MAX(A1:A100)



2) With the same values in columns A and B I have to do another
interpolation for value D1 (refers to data in column B) with this
limitation:

for example: D1 is a value between B56 and B57 -do the interpolation
seeking in A56 and A57 values
D1 is a value between B40 and B41 -do the interpolation
seeking in A40 and A41 values
D1 is a value between B96 and B97 -do the interpolation
seeking in A96 and A97 values

Hope some1 help me...I'm struggling with tons of numbers...