what is wrong am i doing in this code?

[chitalula]

in this code i want to increase the duty ratio until the input volts at RA1 is equal to the Vref, after while loop is true to light the led at portb.5. the problem here is the output is not increase and the duty ratio are not changing to make the output to vary, i need help here to make my code to do as i want

TRISA=255
TRISB=0 
CMCON=%00000101

compOut VAR CMCON.7
VRCON=0
pauseus 10
duty var byte 
duty=0
while (compout=0)
  pwm 7,duty,1
 duty=duty+1
  wend 
  portb.5=1
  pause 100

this is my circuit