Create a new column with several criteria

[cokillerliu]

Need some help on data manipulation.
Original dataset is in column A:G, new dataset should be put in column I :O. The only thing needs to be changed is the price column. I add prime’ to denote new price
1.****** Check May and June prices relationship, if June< May, then (June’- May’)=0.7 and (June+May)=(June’+May’)
2.****** Change Oct, Nov, Dec prices so that Nov’-Oct’=0.2 and Dec’-Nov’=1.5 and Oct’+Nov’+Dec’= Oct+Nov+Dec
3.****** Check Jan and Feb prices, if Jan<Feb, then Jan’-Feb’=1.2 and Jan+Feb=Jan’+Feb’
I want loop these changes but only make changes to the prices that have start and end in the same month.
Any help would be appreciated.

Create a new column with several criteria