I'm forecasting values. I will try my best to explain my requirement.
I have sales data until 2017 and I want to predict sales until 2025. So, my formula for each year sale is Previous year sale value * growth factor and other parameters.
Let's suppose my 2017 sale value is 398000. So, 2018 sale value based on this will be 398000 * growth factor = 2018 Sale value.
2019 sale value will be 2018 sale value * growth factor parameter and so on.
So for every year's sale, last year sale value has to be grabbed and multiplied with growth factor. This is why i asked for the Previous Value function or the Lookup function. Please let me know if there is a better way to do this.
2018 2017 Sale * growth factor
2019 2018 sale* growth factor
2020 2019 sale * growth factor
I hope this explains better.