htaccess wordpress dynamic pages

I have the standard wordpress permalinks set to

/%postname%/

which generates this in htaccess

<IfModule mod_rewrite.c>
RewriteEngine On

RewriteBase /subdomain/
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /subdomain/index.php [L]

</IfModule>

I also have 4 dynamic pages which are currently

http://www.domain.com/subdomain/wordpress-slug/?var=VARIABLE

the site owner doesn’t like this, he wants to see

http://www.domain.com/subdomain/wordpress-slug-VARIABLE/

in the address bar.

My question is, how do I convert http://www.domain.com/subdomain/wordpress-slug-VARIABLE/ back to http://www.domain.com/subdomain/wordpress-slug/?var=VARIABLE so that wordpress knows what to do next?

TIA