Changing the "You need to have the 'comment' right to post a comment"

Hello all, Is it possible to change the message users get when they do not have proper access rights i.e. "You need to have the 'comment' right to post a comment." I restrict comments from anonymous users and I'd like to remind my users that they may need to login. This would save me from answering numerous e-mails about "not being able to post comments." I'd like mine to read like this: You are unable to post a comment because either you have not registered (<-- with a link to the register page) or you are not logged in (<-- with a link to the login page). Is this a change I can make or would an admin have to make the change? Thanks in advance for the help. I appreciate it. - Michael