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.