Does this work?
Code:
P_Val VAR BYTE
TRISB=0

start:
  P_VAL=2  ' RB0=0, RB1=1
  portb = P_VAL
  pause 500
  P_VAL=1 ' RB0=1, RB1=0
  portb = P_VAL
  pause 500
  goto start