Linear Interpolation between non constant intervals

I need a function to find the interpolation between non constant intervals. Is there any function like that in Excel?

I used TREND function but it uses values of a trend line and the declination is way to far of my values and I need too accurate results.

Excel doesn't have a built in linear interpolation function. If you have Quattro Pro, you can use its built in LINTERP function. If you have to use Excel, then you have some work ahead of you.

Linear interpolation isn't difficult in Excel, it's just difficult to do it in a single cell formula. Break it down into mutiple cell steps and it's easy enough:
1) Use the Match function to locate the interval of interest.
2) Use the INDEX function to extract the boundary values.
3) Use the Trend function on the extracted boundary values to calculate y at x.

Originally Posted by MrShorty

Excel doesn't have a built in linear interpolation function. If you have Quattro Pro, you can use its built in LINTERP function. If you have to use Excel, then you have some work ahead of you.

Linear interpolation isn't difficult in Excel, it's just difficult to do it in a single cell formula. Break it down into mutiple cell steps and it's easy enough:
1) Use the Match function to locate the interval of interest.
2) Use the INDEX function to extract the boundary values.
3) Use the Trend function on the extracted boundary values to calculate y at x.

I'm not too familiar with the Excel functions, can you make a simple example please?