Install script
Windows:
Install "EAN-13.jsx" script for Windows: copy files EAN-13.jsx and barcode.png to same folder 
(for example: C:\Program Files\Adobe\Adobe Illustrator CS4\Presets\en_US\Scripts). And install font "ocrb10.otf". That's all. 

MAC OSX
Install "EAN-13.jsx" script for MAC OSX: copy files EAN-13.jsx and barcode.png to "Document" folder. And install font "ocrb10.otf". That's all. 

Work with script:
Open or create new document in Adobe Illustrator. Run "EAN-13.jsx" (File -> Script -> Other scripts... OR press Ctrl+F12). Enter 12 digit your EAN-13 code. Check last control 13 digit and press "Create" button.

Worked on Illustrator CS3-CS5 (Windows and MAC OSX). 