you would probably need a script that generates the dns zone file that creates an address (A) record to your parking web server. Also generate and add the required master/slave entries to your named.conf (assuming use on BIND) then
kill -HUP your nameservers to load the new zone file.
If your document root on your webserver is your parking page, you are done, otherwise, have your script generate a <virtualhost> directive for the domain, add it to httpd.conf and reload apache.
I have a script the generates all these pieces, however I install them manually for now.