edit /etc/httpd/conf/httpd.conf

# Force <DIR> to use SSL
RewriteEngine on
RewriteCond   %{SERVER_PORT}  !^443$
RewriteRule ^/<DIR>(.*)$ https://%{HTTP_HOST}/<DIR>$1 [L,R]

Example:

# Force Nagios to use SSL
RewriteEngine on
RewriteCond   %{SERVER_PORT}  !^443$
RewriteRule ^/nagios(.*)$ https://%{HTTP_HOST}/nagios$1 [L,R]