If you need to change the baud rate during run time do not use defines. Deal with the registers directly.
Code:
X VAR WORD
    START:
     RCSTA.4 = 0 : RCSTA.4 = 1
     RCSTA=$90:TXSTA=$24:SPBRG=129
     HSERIN [dec X]
     HSEROUT [DEC X.7,13]
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