how to get a character based on ANSI code/XSLT

In VB there is a function Chr(), which returns the character associated with the specified ANSI character code.

I need to be able to do the same thing in XSLT, how do I do that?

for instance I'll get an xml item such as this: <lastname>Smith</lastname>

then i'll get the length of the item which in this case is 5

i then need to be able to convert 5 into a corresponding character and display it

Thanks for your help.