Can we create Ipsec Tunnel in Fortigate 110C Configurable Ports?

Hai.

i have Fortigate 110C In my office and i have already used 2 available WAN Ports for two ADSL line,

i want to configure another Lease line for dedicated IPSec VPN. for that can we able to configure VPN tunnel in Configurable Ports (Which is Port 1 to 8) Port 1 & 2 we used for 2 LAN. i have remaining Port 3 to 8.

Please if any one know idea, please share.

Regards,

V.Palanivel