Effective way of calculating the difference

[zzzqinzzz]

Hi all, attached is my sample data. I am trying to find the difference of the values from day-to-day of every column e.g. E, F, E, F for the 4 days.
Any effective way of doing what I am trying to achieve? highlighted yellow is what I have tried.

This is just a small portion of sample data. Data I will be using will be a big big set =]