I have this data
Date Data
8/25/2017 980
8/24/2017 64
8/23/2017 593
8/22/2017 595
8/21/2017
8/20/2017
8/19/2017 794
8/18/2017 437
8/17/2017
8/16/2017
8/15/2017
8/14/2017 629

What if i wanted (794-595)/3 in cell 21st August and 2*(794-595)/3 in cell 22nd August and similarly (629-437)/4 in 17th August, 2*(629-437)/4 in 16th August etc...
How to do this dynamically without regard to the number of missing values in between