Hi everyone

I'm trying to use the =FORECAST(X, Yrange, Xrange) function but have a couple of questions.

My understanding is that either X range or Y range has to be linear, like the number of stocks of a product on each day: e.g.
day(X) stocks(Y)
1 465
2 480
3 420
4 560

Thus, putting X=5 in to the =FORECAST(X,..,..) formula I can estimate what the data(Y) would be on day 5. However, can I use =FORECAST with two non-linear datasets which may/may not affect each other? e.g. I have data on the stock of product A and B in a warehouse:

ProductA (X) ProductB(Y)
152 729
167 811
180 620
192 700

So the two data sets move up or down independently of each other. Can I then put X=170 in to the =FORECAST(X,..,..) function to estimate how many of product B will be in the warehouse given that there are 170 of A? I'm thinking this might not work because it's a pretty advanced estimation for such a basic function, i.e. the relationship is non-linear, they may or may not be correlated etc.

Any ideas? Many many thanks in advance,

AR