how to force/rewrite https connections for a certain directory

I have a directory in a virtual host in which I want to force SSL
connections - the absolute path of that directory is:
/var/www/path1/path2/myapp/admin

The virtual host of concern here is set up in the apache conf file like:
<VirtualHost *>
ServerName applications.domainname.com
ServerAlias www.applications.domainname.com
DocumentRoot /var/www/path1/path2
</VirtualHost>

The virtual host is set up like:
<VirtualHost _default_:443>
DocumentRoot "/var/www/path1/path2"
...

The admininstrative section is of the web site of concern is:
applications.domainname.com/myapp/admin

I want all pages in that directory to be forced to use SSL.

I have tried several means to make this happen including directives in a
directory of the conf file and an .htaccess file. Examples include:

RewriteEngine On
RewriteCond %{HTTPS} !=on
RewriteRule ^/myapp/admin(.*) https://%{SERVER_NAME}/secure$1 [R,L]

and this in an .htaccess

RewriteRule ^(.*) https://%{SERVER_NAME}/$1 [R,L]

Any ideas are MUCH appreciated!