Whats the formula to look at data in precentages in fixed periods

[donald]

how do I calculate a continous percentage return of two data points at fixed
intervals? example : data set={12,50,03,59,22,....} , fixed
interval=2periods.
[(12-03)/12], [(50-59)/50], [(03-22)/03],....I'd like to do this in Excel 03

 

[Max]

how do I calculate a continous percentage return
of two data points at fixed intervals?
example : data set={12,50,03,59,22,....} ,
fixed interval=2periods.
[(12-03)/12], [(50-59)/50], [(03-22)/03],

Assuming data is in A2 down: 12,50,3,59,22,...
In B2: =(A2-A4)/A2
B2 formatted as percentage, then copied down