Trick Mac into thinking an external display is connected

Okay, so I know this is a little specialized of a question, but the same answer should apply to a single computer with a single display. I have a Mac Pro with an HD Radeon 5770 video card as well as another video imput/output card. Currently, I'm running five displays on the MacPro using a software to span 5 video elements into one massive video. That works fine, my question is whether I can "trick" my Mac Pro in to thinking it has another (sixth) display connected to my HDMI video output (which is on one of my video cards). There are two reasons I want to do this: (1) I need an additional monitor for the live configuration panel in my video software, and (2) I really don't want to connect a HDMI TV/Monitor to this output to use since I wouldn't be able to see it anyway. See, I have this machine mounted in a server area (which is not accessible) and the machine is only accessed via Apple Remote Desktop (or sometimes screen sharing for minor changes). Attaching a monitor seems rediculous if all I really want to do is basically create a virtual monitor to use for ARD, since I will never be able to see the physical monitor.

So, in essence, I want to make the computer think a display is connected so that I can use that virtual display in ARD. I would have to assume that since I have an additional video out, the computer should be able to think it has another display attached to that card. Otherwise, if there is just some other way to create a virtual monitor which would be recognized by the computer that would be fine as well. So, while this seems specialized (that I want a sixth monitor), what I really need is just one more virtual monitor for ARD. Thanks!