> I also tried:
>    movlw 01h
>    btfsc MyFlags, Complement_Carry
>     xorwf STATUS, F
>
> but it didn't work.  I was hoping that the xorwf instruction would
> operate as normal and change the carry flag and afterwards set the Z flag
> if the result was 0, but C is totally protected from being modified.
>
> Has anyone got a better approach (preferably one that does not need a
> file register)?  Maybe its staring me in the face, but right now I'm
> staring at the insides of my eyelids :-O

Perhaps:
        rlf     FSR
        movlw   1       ; Could also be movf flag,w ...
        xorwf   FSR
        rrf     FSR

Note that when all is said and done FSR will have the same value it
started with, Z will almost certainly be cleared, carry will be toggled,
and nothing else will be affected.