OK...

Chip, you can download and add this project to your solution:
http://www.netindustry.nl/resources/xsltextensions/default.aspx?lang=en

follow instructions there to enable it.

Afterwards, take these steps:
- Add a reference to Vitsol.XsltExtensions

add these lines to the Kentico.CMS.Contentengine/ContentProvider.cs in the Transform() method, right before the transformation:

// Get the settings for the XsltExtensionFactory section
XsltArgumentList argumentList = new XsltArgumentList();
XsltExtensionFactory factory = new XsltExtensionFactory();
factory.AddObjectsTo(argumentList);

and replace this:

xslTransform.Transform(xslDoc, null, resultSW, null);

with this:

xslTransform.Transform(xslDoc, argumentList, resultSW, null);