removeChild Problem

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.
.
	addChild(mc);
	
	if (mc.y <= 0) {
		removeChild(mc);
	}
.
.
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this code is supposed to remove the movieclip if it goes on the top side outside of the movie which is negative Y value. For some reason the movie clip goes into the negative value and it is still there…if anyone can give me some tips it would be appreciated thanks