Maybe the bitname RP0 isn't predefined for some reason. Try this instead.

Code:
asm
    bsf STATUS, 5
    call 03ffh
    movwf OSCCAL
    bcf STATUS, 5
endasm
Scroll down to the last line in the window "Address - Program Code". The Line should look similar to this .....

03F8: 3FFF 3FFF 3FFF 3FFF 3FFF 3FFF 3FFF 3474 ÿÿÿÿÿÿÿt

As you can see the last memorylocation contains 3474 instead of 3FFF. That's your calibrationvalue, if its 3FF you've managed to erase it. You can recover it if you have a frequencymeter and are prepared to do the work involved. Not difficult but timeconsuming.

/Ingvar