Yes, and use CONF FULL VLS before switching to CONF 3 in the MCDU pagewhen landing with a delta VRef with CONF 3:
1st. insert the intended FPLN
2nd. See CONF FULL VLS in the MCDU
3rd. Add delta VREF and corrections if applicable
4th. Insert that value in VAPP field
5th. Select CONF 3 in the MCDU
You will also need to select GPWS FLAP 3 mode, in the 320 family.
Good luck in the check!