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I don't understand the question. Are you saying you want to leave the dvi hooked up and be able to display the images on the tv screen, but also be able to stop the images from displaying on the tv and instead display on the Mac, but without unplugging? If so, go into system prefs and go to displays, this should allow you to do what I think you are asking about.
 
the best i can think of is to turn on mirroring when you want to turn it off and turn off mirroring when you want to have 2 seperate displays.

mirroring will give you your main screen as per regular and the mirror will still be transmitting but it won't significantly interfere with your primary monitor
 
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