How specify css file?

I've looked and the program seems to have the capability to specify a separate css file (which will format the final .doc output file) but I can't get it to work.

I've tried to specify the css file in the clsMsDocGenerator.php file at:

function clsMsDocGenerator($pageOrientation = 'PORTRAIT', $pageType = 'A4', $cssFile = '/home/user/public_html/file.css');

and in that file.css I specify a format:

#greenFormat {
color: #00ff00;
}

and in the file which creates the .doc file I specify both the file location and #greenFormat:

$doc = new clsMsDocGenerator('PORTRAIT', 'A4', '/home/user/public_html/file.css');

$greenFormat = array('style' => '#greenFormat');

but I can never get the .doc generator to obey the separate file.css

I'm sure I'm doing something simple wrong - but I don't know the correct syntax. Any ideas?