Changing CSS on a per page basis

Hi folks, I’m working on a theme currently that requires the post content section to have different widths on different pages.

Currently, this is the code I’m working with.

#contentContainer {width:510px;}
#contentTextContainer {with:80%; margin:auto;}
#contentTop {width: 510px; height:15px; background-image:url('images/contentrecTop.png');background-repeat:no-repeat;}
#contentText {width:510px; background-repeat: repeat-y; background-image:url('images/contentRecmiddle.png');}
#contentBottom {width: 510px; height:15px; background-image:url('images/contentrecBottom.png'); background-repeat:no-repeat;}

What I would like to be able to do is change the width of the container, and thus the width of the content inside that container as well, possibly based on page-ID, or based on a custom field if that is possible.

Anyone have any idea how I might be able to do this?

dave