Fortigate 60E PPPOE configuration

Hi all, first of all thank you in advance for the ideas and solutions.

1. i have 5 static IP from my IPS

2. i configure a PPPOE link in my 60e

3. 60e automatically detect my first static IP

4. but i do not want the first static IP to be used by the firewall i wanted the 3rd static ip to be use.

Can i know if there is a way for me to configure static ip on my PPPOE configuration.

THanks!! =)