There is a "Skin Widget" that will do the trick.
If you download the Minimal Extropy skin (
http://dnnskins.codeplex.com/releas...iew/73347) you can install it on your site and see how it is used. Examine the skin file for details.
Here is a discussion of adding the text size skin widget to the Dark Knight skin:
http://www.dotnetnuke.com/Resources...posts.aspx