playback volume - can i alter between staves?

hey folks

ive a couple of pieces i've written that require a fairly large volume difference between the staves in the piano part. The bass clef part is supposed to be played very languidly and quietly while the treble cleff is punchy and LOUD. I can do everything i need for the punchiness via the accent markers, but the volume differences (pp for bass cleff and mp or mf for treble clef) dont seem to hold, even though they appear in the score.

is there a way to get this working or am i missing something?

thanks