I'm trying to set up my domain as follows, but I'm not actually sure if it's possible.

I have a domain where I would like the base and www addresses to go to my static site, but others to go to my application server. For example:

My domain is registered with Dreamhost, and my application is on a VPS at Webbynode. I've set up the domain in Dreamhost to use Webbynode's nameservers:

ns1.dnswebby.com
ns2.dnswebby.com
ns3.dnswebby.com

And in Webbynode I've set up a wildcard A record to point to the IP address of my VPS:

*  1.2.3.4  A

and this works nicely, if I go to app.example.com it resolves to my application server at Webbynode.

However, what I'd like to do is have example.com and www.example.com go to my static site, hosted back at Dreamhost, whilst still having any other domain go to my app. What I've done to try and achieve this is set up these DNS "NS" entries at Webbynode, trying to get Dreamhost to resolve these domain names:

(empty)  ns1.dreamhost.com  NS
(empty)  ns2.dreamhost.com  NS
(empty)  ns3.dreamhost.com  NS
www      ns1.dreamhost.com  NS
www      ns2.dreamhost.com  NS
www      ns3.dreamhost.com  NS

(I don't have a fixed IP address at Dreamhost so I can't just set up simple A records).

However this doesn't work... does anyone have any idea if this is possible and if so how it could be done?

Update:

I've got this working now, as above for the domain (i.e. registered with Dreamhost, but using Webbynode's nameservers). To delegate the DNS for www.example.com to Dreamhost, I've got the following DNS entries set up:

www.example.com.      ns1.dreamhost.com.  NS
www.example.com.      ns2.dreamhost.com.  NS
www.example.com.      ns3.dreamhost.com.  NS

(note the full stops at the end)

And to get example.com to resolve to my static site, I set up CNAME record:

example.com.   www.example.com.   CNAME

So now, example.com and www.example.com go to my static site on Dreamhost, and if they change the IP address of my shared hosting it won't affect me, and all other subdomains go to my application server.

This seems to work nicely, but if anyone knows a better way to do it I'd be happy to hear it.

Thanks to all who replied.