Selecting 400 characters before a string such as YYY i

Hi,

I need to select 400 characters before a string such as YYY in a
larger text document.

I've in the past reversed the content to then find the 400 characters
before YYY using regex effectively however I'm wondering if there is a
better perhaps simpler way to do this in xslt?


Thanks


--
Alex

An informal recording with one mic under a tree leads to some pretty
sweet acoustic sounds.
https://sites.google.com/site/greigconteh/albums/diabarte-and-sons