Q: pc & imac sharing monitors

i have a windows 7 PC with a 30" apple cinema display attached to it.  i would like to attach a iMac as a second monitor & then use either the PC or the iMac to drive both monitors.    i.e.- i would like to turn my pc on and use the cinema display as my primary monitor and my iMac as my secondary monitor or i would like to turn my imac on and use my cinema display as a secondary monitor to my iMac. i would like to do this without unplugging and plugging cables all the time.