XSLT to convert an XML element containing RTF data to HTML?

OK, so here's the background:

We have a third-party piece of software that does a lot of complicated stuff to generate an XML file from a lot of tables based on a wide array of business rules. The software allows you to apply an XSL transformation by supplying an XSLT file as part of its workflow, before continuing on in the process, which is usually an upload to one or more servers, based on more business rules.

Here's the problem:

One of the elements (with more on the way) this application is processing contains RTF text, and needs to be converted into formatted HTML before being uploaded. There are no means of transforming the XML inside the application other than through an XSLT file, and once we output the file, we cannot resume the workflow. My original thought was, "Easy! someone must have written a few XSL transforms for converting RTF to formatted HTML!" Hours of searching later, I must conclude I either suck at searching or it's awfully obscure.

Disclaimers:

• I know the software is pretty darned limited; I'm stuck with it.
• I know there are a lot of third-party tools to do this; they are not available to me because I would need to run them externally.
• I know that this is not a pretty or efficient thing to do with XSLT. Changing that is not an option for me at this point.

If I cannot find a means to do this through pure XSL transforms, I will need to output the files locally, run the extra process, and take the destination routing on through a custom proces开发者_运维百科s. I really don't want to do that.

Does anyone have access to an XSL transformation function/ scheme that will allow me to do this natively in the application? Perhaps a series of regular expressions I could use or something?

So it turns out that external scripts can be invoked from the XSLT. It seems I will be using another scripting language to get this to work. I'm a little bummed there was no other answer available.