It's a way of showing that you are not interested in someone's opinion or what s/he said does not appeal to you at that particular moment.The one who says this uses a rather sarcastic tone to express his/her disinterest in the topic.
Faddy: Hey,I just saw Avatar on was awesome!

Gabby (really doesn't give a damn about the movie): Ah ok! What time is it right now?

Faddy: Dude,you are not interested,that's not cool,you are changing the topic now.
by DonDjibril April 16, 2010
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