[xsl] escaping/entities on the fly?

["Gabriel K." <gabriel.klappenbach@xxxxxxxxxxxx>]

I'm creating an URL (a mailto: link) that uses characters not allowed, 
encoded in ISO-8859-1. The characters are for instance e d v.
So when when you click the mailto link and a new mail is created, these 
characters in the subject line are not readable.

Is there a function or some other way to convert for instance the character 
"e" to  å or it's entity number  å on the fly?
I don't want to have these (entities) in the XML file.

/Gabriel