If this is a book Wiley purchased along with the WROX name (The list can be found on the Book List link above) you can find the code on this site. Click "Download Code" on the links above.
If the book in question is no longer in the Wrox booklist you will need to visit www.apress.com
and download the code from them. Last check they had most, if not all, of the books they bought availible online.
Unemployed (Thanks GWB)
NOT a Wiley/Wrox Employee