Dedicated IP for VPN Service

Is there a way to set a dedicated IP on which my VPN service will run on? For example: My server IP: A.B.C.D and I have another IP on the same machine: A.B.C.E Right now, I can only connect to my VPN using the IP A.B.C.D but I would like to connect using the IP A.B.C.E instead. What I want to do can be done in the web server by simply selecting the IP address from a drop-down menu (Web>Settings>Edit), but I want to do it for the VPN. Is there a config file somewhere that I can edit or something I can do in order to have my VPN service running on A.B.C.E? Thank you! Leppy-