if you have public ip. what you can do is you can use the DDNS function of your router or use the DDNS function of your DVR if you dont have a router.
if you have a private ip. what you can do is use the vpn software hamachi and you need port tunnel to use Dedicated DVR.
the setup will will be like this. you need a computer running vpn software and port tunnel. and a dvr connected on the network together with the computer. the vpn software will enable you to see the computer with private ip and the port tunnel software will forward you to the DVR when you access the computer.
for PC based system. installing hamachi vpn software will do.
Note: client side must install hamachi and must be with the same group to be able to access the dvr.