S90 ES question: Can I transpose one element by itself?

[Aaron Trimble]

Hi, on my S90 ES, I know there has to be a way to split the keyboard with multiple sounds and transpose one sound while leaving the other(s) the same . Specifically, I am in Performance mode with 3 voices and want B6 and down to play Piano and a string sound and C6 and up to play a bell sound transposed down one octive. Any ideas?