How can I adjust sound level when streaming radio from my Apple TV through Airplay speakers?

I have a 2nd Gen Apple TV with an airport express set up as airplay speakers. I can stream the new radio through using the Airplay speakers pretty well. The problem is that once I've got it going, I cannot adjust the sound level without laboriously backing out of the radio menu, going back to the top level menu then drilling down into the Airplay settings to raise or lower the speaker's sound level.

Is there an easier way to do this?