Subtracting one record value from another (1 Viewer)

[Malachy39]

I have a column in a query "Meter Read". It lists the meter reads of a printer on various days. For example 4000 on one day and then 4016 on the next day. 4132 on the next. How do I build an expression so that it reads the difference between each day?

i.e. the first record will show 0, and the second record will show 16 the third will show 116.

Thanks