I have a 2 column S/S detailing monthly electrical meter readings .

The first column consists of the meter digital readout each month.

I would like the second column to subtract the previous month's
digital readout in column 1 from the present month's readout in
column 1 and enter this difference in column 2 opposite each months
reading as it occurs in column 1.

Thus , say , I would have a reading of 24543 against May in column 1
and another reading of , say , 24785 against June in column 1.

I require a formula which will show the increase between these 2
readings and place it against the June row in column 2.

What formula do I need to do this , please ?

B.N.