I don't have Dreamweaver, but I suppose that its regex engine doesn't support lookaround - at least this introduction from Adobe doesn't mention it. So you'll need a workaround. One thing you could do (not pretty, but it works):
Use © $1QQQQ2009 as your replacement string, and then do a second pass, searching for QQQQ and replacing that with nothing. As long as you're sure that you don't have any real occurences of QQQQ in your text somewhere :)
Tim Pietzcker
2009-11-16 21:10:01