Adjusting volume after automation is written

[rock15478]

Hi, I've been wondering this for quite some time now...I'm not even sure if it's possible. Let's say in the middle of mixing a song, I want to fade the guitars down at a certain point, and then fade them back up. I'd normally do this with volume automation. However, let's say a week later I want to change the overall volume of that track, but keep the automation. Is this possible? Whenever I try to change the volume on a track where automation is written, it slides the fader back to its original position. I guess I'm wondering if there's a way to proportionaly keep the automation in relation to the volume changes. Any help would be greatly appreciated. Thanks