If you have been granted the appropriate
override in the httpd.conf you will be able to do it in .htaccess. If you don't have that override permission you won't be able to do it without access to the httpd.conf.
in the section of the httpd.conf for your site will grant you the permission to set error pages in .htaccess. If there is already an AllowOverride entry then add FileInfo to the existing one.
Contact the person who has control over the httpd.conf file and ask if they will add that permission.