Adding distribution to data table with cumulative sum

[plantaddict]

Hi, I would really appreciate some urgent help on this please as I'm so stuck.

I currently have a few rows of data and I'm looking to shift the data by a month, apply some distribution probabilities based on how many months have elapsed and sum cumulatively.
Say I have a distribution table with 4 probabilities being: t=1 is 40%, t=2 is 30%, t=3 is 20% and t = 4 is 10%.

Data is shown below:

Oct 20	Nov 20	Dec 20	Jan 21	Feb 21	Mar 21
20	30	25	40
25	55	50	70	80
	35	45	75	50

I'm looking for a formula that would automate the following:

Oct 20	Nov 20	Dec 20	Jan 21	Feb 21	Mar 21
	=20*40%	=(20*30%)+(30*40%)	=(20*20%)+(30*30%)+(25*40%)	=(20*10%)+(30*20%)+(25*30%)+(40*40%)	=(30*10%)+(25*20%)+(40*30%)
	=25*40%	=(25*30%)+(55*40%)	=(25*20%)+(55*30%)+(50*40%)	=(25*10%)+(55*20%)+(50*30%)+(70*40%)	=(55*10%)+(50*20%)+(70*30%)+(80*40%)
		=35*40%	=(35*30%)+(45*40%)	=(35*20%)+(45*30%)+(75*40%)	=(35*10%)+(45*20%)+(75*30%)+(50*40%)

 

[plantaddict]

Any help would be very much appreciated! Thank you so much