Difference of two different fields in two different rows

[#1]

How get difference of ((A of Start Reading(08/10/2013)) - (A of Stop Reading(07/10/2013))

for table given bellow

	Start Reading	Stop Reading	Date
A	5000	5200	07/10/2013
B	3800	4000	07/10/2013
A	5800	7000	08/10/2013
B	5300	8000	08/10/2013

[bbi_mba_76]

Hi,

maybe you could modify your script to get the previous stop reading value.