Custom DNS with a subdomain using GoDaddy TotalDNS Control

I've seen a handful of other threads regarding this topic, but following them did not solve my problem...

Here's the situation:

I have a domain registered at http://godaddy.com
I have purchased a Custom DNS service here at DynDNS for my domain name (example.com)
I would now like to delegate just a subdomain to DynDNS to be used for tracking a dynamic IP (home.example.com)

Here at DynDNS, under my 'example.com' Custom DNS Zone, I added an A Record for http://home.example.com, and it is properly tracking my IP address (using DynDNS Updater Client)

At GoDaddy, the nameservers for 'example.com' are http://ns31.domaincontrol.com & http://ns32.domaincontrol.com, allowing me to use their TotalDNS control utility. From there, I added Nameserver records for the 'home' subdomain, pointing them to the DynDNS servers.

Here is what the nameservers section of my zone file looks like:

; NS Records
@      3600 IN  NS  http://ns31.domaincontrol.com
@      3600 IN  NS  http://ns32.domaincontrol.com
home    1800    IN  NS  http://ns1.mydyndns.org
home    1800    IN  NS  http://ns2.mydyndns.org
home    1800    IN  NS  http://ns3.mydyndns.org
home    1800    IN  NS  http://ns4.mydyndns.org
home    1800    IN  NS  http://ns5.mydyndns.org

I thought that this would be sufficient. But my Custom DNS service is currently inactive since it sees http://example.com pointing to other nameservers. It doesn't seem to care that the subdomain 'home.example.com' is delegated to DynDNS.

Do I have to purchase another Custom DNS Service for just the subdomain itself, or am I missing something else entirely?

Thanks for any help!

-Tom