Yes, of course!! Each and every note on a piano - upright, grand, and most electronics these days, are separate entities, with their own dynamics.
There are some pieces which need the l.h. to play the melody, while the r.h. plays an accompaniment, so yes, not only is it possible, it's obligatory!
It's even necessary in some pieces for an individual hand to play notes (with different fingers) at different volumes, and certainly, concert pianists, and even those at grade V and above, will be able to achieve this. The same goes for staccato/legato notes. Go ahead and indicate what dynamics each hand must use, individually. We pianists are quite used to being directed thus!
In fact, years ago, when a lot of electronic pianos were not touch sensitive, I found it very difficult to play 'properly' - just because every note came out at the same volume, both hands. Thank goodness they've advanced!