Style Sheet Assistant is a PageSpinner helper application included with PageSpinner that will let let you create Cascading Sheet Standard Level 1 definitions.
Please note that Style Sheet Assistant is still under development, since Explorer and Navigator has both bugs and different ways of implementing the Cascading Sheet Standard Level 1 recommendation by W3C.
Since StyleSheet Assistant is part of the Style Sheet menu extension you should be able to download future updates to the extension and application from the net. Go to the Support Page at PageSpinner's web site to find information about updates of Style Sheet Assistant. Style Sheet Assistant requires that AppleScript is installed in the system.
Style Sheet Assistant is written with FaceSpan, an interface builder for AppleScript.