Does the following code, right?
domain: shop.qupple.net (shop subdomain)
############################################
enable rewrites
Options +FollowSymLinks
RewriteEngine on
RewriteCond %{REQUEST_URI} !^/shop/
RewriteRule ^(.*)$ /shop/$1
############################################
you can put here your magento root folder
path relative to web root
#RewriteBase /magento/