from the book :- pwm pin,duty,cycle [ it says pin can be a constant or var from 0 to 15] whwre portb.0 = 0
therefore this may work , I have not tested it

for Avar=0 to 7
cycle=4
for Duty=0 to 220 step 1
pwm Avar,Duty,cycle
next Duty
cycle=1
for Duty=220 to 0 step -2
pwm Avar,Duty,cycle
next Duty
low Avar ;end of routine