How can reduce short description from my "Highlight " items (home page)

[JOE]

I need to reduce the description in the principal page "Highlight items"
I can deduce that is displayed by a function like "LENGTH", 'TRIM" the first 40 characters.
you can see some like this "New Ipod bla bla bla ...". after three dots.

thank you in advanced

p.d. excuseme my english but i prefer to do my question here because there are more users in forum english that spanish.