How can I make a sub-domain point to a dynamic IP and the rest of the domain as it is hosted on a server with static IP?

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http://serverfault.com – Basically, I have a domain mydomain.com hosted by a certain hosting company on its servers. I have access to the cpanel and can make changes a s per required. However, I want to host a dvr remote interface on one of its pages. The DVR is in my office which has a dynamic IP address. I first thought of using the numerous free DDNS services available. But then since I already own a domain name I thought of using that one. How do I do it? (HowTos)