16F690 VREF PGC question

On the PIC16F690 RA1 is both the ISPCLK (PGC) and VREF pin

i need to use an external VREF and am concerned about conflict with ISP operations

VREF would be 2.5V and would connected to the 'cathode' (and adjust pin) of a TL431 which would be fed from a 1.2K resistor at 3.3V

do you think with the MEL USB programmer i use i will be able to drive the ISPCLK line to program the chip given the attached circuit i described ?

one more complication
i usually put a cap on the VREF but i suppose that will have to go away as it would ruin the ISP clk

any experience or comments would be much appreciated, thanks