Please use the code tags when posting code to preserve the indentaton. The following will move the avatar's arm.
Code:
import viz
viz.go()
female = viz.add('vcc_female.cfg', pos = [0,0,5], euler = [180,0,0])
female.state(1)
def tossBall():
forearm = female.getBone('Bip01 R Forearm')
forearm.lock()
forearm.setEuler(90,0,-90)
vizact.onkeydown('b', tossBall)