Xbox 360 Rock band gutiar question. The controller wored great hooked right up downloaded drivers off and going. SNAG cant seem to map the whammy bar, what key is it supposed to be mapped to is it the Killswitch or what...thanks to anyone who can help.

Xbox 360 rock band controller. I have the controller hooked up and mapped fine everythign works EXCEPT the whammy bar. Cant seem to figure out which key it is so I can map it. Can anyone help I thought it was the kill switch but seems to give me confict already used. Appericate any help you can offer.