.htaccess - 301 SEO redirect on single pages

I have the following .htaccess for my CMS Made Simple web site.

Now I want to move some articles from my article-section on the web site to my blog - therefore I would like to do something like this:

redirect 301 http://www.mydomain.com/articles/my-article http://www.mydomain.com/blog/my-article

But this does not work with my .htaccess - any idea why? - or how to solve the problem?

Mydomain.com - is a CMS Made Simple web site
Mydomain.com/blog - is a WordPress blog

I really hope someone can tell me how to do redirects on single pages that I have to move and still use this .htaccess

***************************************************
Here is my .htaccess
***************************************************

Options +FollowSymLinks
RewriteEngine on
RewriteBase /

# 301 Redirect all requests that don't contain a dot or trailing slash to
# include a trailing slash
RewriteCond %{REQUEST_URI} !/$
RewriteCond %{REQUEST_URI} !\.
RewriteRule ^(.*) %{REQUEST_URI}/ [R=301,L]
RewriteCond %{HTTP_HOST} ^mydomain.dk
RewriteRule (.*) http://www.mydomain.dk/$1 [R=301,L]


# URL Filtering helps stop some hack attempts
#IF the URI contains a "http:"

RewriteCond %{QUERY_STRING} http\: [OR]

#OR if the URI contains a "["

RewriteCond %{QUERY_STRING} \[ [OR]

#OR if the URI contains a "]"

RewriteCond %{QUERY_STRING} \] [OR]

#OR if the URI contains a "<script>"

RewriteCond %{QUERY_STRING} (\<|%3C).*script.*(\>|%3E) [NC,OR]

#OR script trying to set a PHP GLOBALS variable via URL

RewriteCond %{QUERY_STRING} GLOBALS(=|\[|\%[0-9A-Z]{0,2}) [OR]

#OR any script trying to modify a _REQUEST variable via URL

RewriteCond %{QUERY_STRING} _REQUEST(=|\[|\%[0-9A-Z]{0,2})
RewriteRule ^.*$ - [F,L]

# END Filtering

# CMSMS Rewriting - Rewrites urls in the form of /parent/child/
# but only rewrites if the requested URL is not a file or directory
# Set assume mod_rewrite to true in config.php and clear CMSMS cache

RewriteCond %{REQUEST_FILENAME} !-f [NC]
RewriteCond %{REQUEST_FILENAME} !-d [NC]
RewriteRule ^(.+)$ index.php?page=$1 [QSA]

**************
Thanks in advance

Redirect with mod_rewrite
RewriteRule ^old$ http://www.mydomain.com/new [R=301,L]

Options +FollowSymLinks

RewriteEngine On

# Redirects.
RewriteRule ^articles/my-article/?$ http://www.mydomain.com/blog/my-article [R=301,L]

# 301 Redirect all requests that aren't a file to
# include a trailing slash
RewriteCond %{SCRIPT_FILENAME} !-f
RewriteRule [^/]$ http://www.example.dk%{REQUEST_URI}/ [R=301,L]

# Force www.
RewriteCond %{HTTP_HOST} ^(example\.dk)$ [NC]
RewriteRule ^(.*)$ http://www.%1/$1 [R=301,L]

# URL Filtering helps stop some hack attempts
RewriteCond %{QUERY_STRING} (http\:|\[|\]) [NC,OR]
RewriteCond %{QUERY_STRING} (\<|%3C).*script.*(\>|%3E) [NC,OR]
RewriteCond %{QUERY_STRING} (GLOBALS|_REQUEST)(=|\[|\%[0-9A-Z]{0,2}) [NC]
RewriteRule .* - [F,L]
# END Filtering

# CMSMS Rewriting - Rewrites urls in the form of /parent/child/
# but only rewrites if the requested URL is not a file or directory
# Set assume mod_rewrite to true in config.php and clear CMSMS cache
RewriteCond %{SCRIPT_FILENAME} !-f [NC]
RewriteCond %{SCRIPT_FILENAME} !-d [NC]
RewriteRule ^(.+)$ /index.php?page=$1 [QSA,L]