.htaccess for addon domain

I have www.a.com (main), and addon domain www.b.com

Structure directory domain b is www.a.com/b.com

i want to make .htaccess setting : www.b.com/prod_detail.php?Code=200 and 开发者_JAVA百科be www.b.com/prod_detail/200

if i sett like this :

RewriteEngine On
RewriteRule ^prod_detail/([0-9][0-9])/$ /prod_detail.php?Code=$1

not working. Why? Thanks

---

This seems like it would only match 2 digit numbers, how about this instead:

RewriteEngine On
RewriteRule ^prod_detail/(\d+)$ /prod_detail.php?Code=$1