Quantize a song

If I have a song how can I efficiently quantize it? If, say, the song hovers around X bpm, possibly being significantly different at the end of the song than at the start, how can I quantize the size easily so that I can put a metronome to the song and it be in time? In my case I sort of want to convert whatever the tempo of the song really is to X bpm. In cubase I can do this by hand using warp points and simply stretch beats. It's not the best way though because mistakes can be costly, possibly requiring one to start over from scratch.

Serious recommendation: DO NOT!!!

Serious suggestion here: If you're going to reply to someones question please do it with an answer.

In addition to what cc has said, you can also do the stretching using dual-stretch which is in principle a bit similar to warp markers.