Question about cello double stops?

If I want to write a passage that includes two long suspended notes
(played as a double stop on the cello) how hard would it be on the
performer if I dictated one dynamic for one note and another dynamic
for the other note. In this case, I want one note as ppp and the other
as p. Obviously it wouldn't be possible to play one note fff and
another pp for example but I was wondering if what I want is ok.