Trick PC into having a physical and virtual DVD Drive

At school, I've got a server ruing to which I can make a VPN. Now, I need to set up a few VM's with all having a need for a different OS.

I can't physically go to school to change a boot DVD, so I need a way to trick that server into thinking it has two DVD drives plugged into it. One is a physical one, the other (preferably) a mounted ISO file, so I can use both as boot DVD for the different VM's. (Say Ubuntu Server for some ones and Windows 7 for others).

Is there any way of doing this?

Regards