Question about units and formulas

[nickapos]

Hello to everyone,

I have two questions. First question is it possible to define custom units in hp prime?

Second question is it possible to use units in equations and if yes what is the best way to do this?
I.e in a formula E=πR^2 should I assign the unit in the actual value I.e 2_m or to the R? I.e R_m?
I think that the first might be the right way but I wonder if the second is possible as well?

Thank you very much