http://www.dyndns.com/
That will help.
Basically, you setup an account .. Install a client util on your PC .. It will detect any WAN IP changes, send those changes up to DynDNS, where you have an address like
http://wrx.gotdns.org/
The client will always make sure that URL resolves to your current WAN IP Address.
Simple? Yes!
Open port 80 up on your Router to the Interal IP of your DVR.
Or you could save yourself the pain/frustration and ask your ISP for a Static IP.
Bobs yer mothers brother.