Mean temperature for each depth layer

I have a datasheet with temperatures over different depths like 1.2, 1.6, 2.1..and so on. What I would like to do is to get the average temperature in a vertical cell of 1 m, eg: layer 1-2= (1.2 1.6)/2.

Of course I know I can do this manually, but that will take alot of time. Is there a shortcut in excel or should I move on to an R programming forum?

Thanks in advance for any help!

Radiator