Hi,
I have an excel sheet that has columns as Jan, Feb, March up to December as shown in the image below.

I would like to calculate the difference between A & B (A-B) for January, February, up to December on row 4, then the difference between C&D (C-D) for January, February up to December on row 7. I would like to follow the same pattern up to row 730.
Can somebody please suggest a macro-free way of performing the calculations?
Thank you in advance!