MrShortly thank for your rapid response..... I have already done the LOGEST() and I have already the coefficients A and B.

But now how can I solve the algebra problem??? Is there a Function for that???

Another thing is, but it´s for later, the data is given from web and I want to copy paste the values in a way like the ones that I put here (top down)..... So the range that I put in the LOGEST() function is not estatic. The range is always growing. So this function might not work for what I want. Maybe with some VBA code.

But first I need to figure how this function works, so I can put the problem to the VBA gurus.......