292360
OK, I'm sorry I didn't read carefully enough what you intended to do before I posted. You want everything to happen in that link (i.e. not go to some other page first). You solution should work, though I think it is a little insecure because it will be very easy for your visitors to figure out the URL and start spamming you (if you have a small trusted userbase this may not be a problem).
I would suggest instead, wrapping a tiny HTML form around the link, and make the link a *button* instead. This way the message will be set as a POST var. Then your change isn't needed, and security is improved.