This is not a good idea at all. And destroying this functionality could remove some users from your system. I am talking mostly of the handicaped people that use some other form of writing then a keyboard. There are oftwen shortcut's for their email, name, ect. Not allowing these to be pasted in would be a huge annoyance.
That and you have to remember that Ctrl-V, while default on windows boxes, is not the only key combination that is used or can be used.
Note: I do not test code. I just write it off the top of my head. There might be bugs in it! But if any thing I gave you the overall theory of what you need to accomplish. Also there are plenty of other ways to accomplish this same thing. I just gave one example of it. Other ways might be faster and more efficient.