.htaccess problem

Hello

We have a client running 100+ domains on their dedicated server under a single cpanel account

apache looks like this

Master domain /home/username/public_html/
addon domains: /home/username/public_html/addon-domain/

we want to lock down wp-login.php and wp-admin to certain IPs

if we add to htaccess in each domains folder:

#allow wp-admin to selected IPs
<IfModule mod_rewrite.c>
RewriteEngine on
RewriteCond %{REQUEST_URI} ^(.*)?wp-login\.php(.*)$ [OR]
RewriteCond %{REQUEST_URI} ^(.*)?wp-admin$
RewriteCond %{REMOTE_ADDR} !^1\.2\.3\.4$
RewriteRule ^(.*)$ - [R=403,L]
</IfModule> 

then this fixes it, however their is over 100 installs and if an IP changes we want a quick way to update it.

I tried adding it to /home/username/.htacess however it doesn’t appear to work no doubt due to an error in the content.

can someone help me change the above to work on all domains/sub-files/folders that match wp-login/wp-admin so we have just a single .htaccess file to control this?