Using my HDMI cord, can I have it lock to one screen for my tv and a different one on my computer?

I have the cord from iWires. I want to watch something from one screen on the tv (why I bought the long cord) and then do some homework on the other screen. Is there a way in the settings to lock the tv to one screen an then do whatever else I need to on the computer?

Computer is a MacbookPro. Thanks for the help anyone can provide.