develope extension loading custom css

[GunFood]

Hi,

I try to develope an extension for my favorite antispam engine eXpurgate (http://www.eleven.de/expurgate-anti-spam.675.html). The GUI looks fine so far, I have to deal with the custom configfile, but that's solvable. But now I woud like to add a custom css file to show notification boxes. These boxes are only needed inside my extension, so I don't want to set them into global.css. I placed the css and a few images inside /admin/htdocs/modules/expurgate, but they don't get loaded. The extension documentation is quiet poor, so maybe someone have an idea, how to solve this.

Thanks

Rene Suhle