Adding a CSS

A friend referred me to your fine site, and I am very impressed with the quality of the rich text editor.  I am evaluating it for use within my site, and I have one question:

 

I am currently using an RTE of my own design that is an amalgam of scripts, and pages that I have created, or harvested through sample sites, etc.  I use it to create HTML-snippets that are stored in a DB, and then rendered.  The rendering process may attach any of a number of CSS files to the final document.  As such, some backgrounds may be dark, and cause the text to become invisible. 

 

Is there a way that I can attach the CSS that will be used in the rendering to the textbox so that it will display while editing?

 

Thanks

Lance