I wouldn't try to combine results from multiple DNS servers with differing configurations, in the way you suggested.
Standard DNS
You can do this with normal DNS server software (e.g. BIND). One way involves a lot of work maintaining a list of blocked domains:
The suggestion at this site is to edit the config file to include
zone "ads.x10.com" { type master; file "dummy-block"; }; zone "advertising.com" { type master; file "dummy-block"; }; zone "amazingmedia.com" { type master; file "dummy-block"; }; zone "clickagents.com" { type master; file "dummy-block"; }; zone "commission-junction.com" { type master; file "dummy-block"; }; where dummy-block is
$TTL 24h @ IN SOA server.yourdomain.com. hostmaster.yourdomain.com. ( 2003052800 86400 300 604800 3600 ) @ IN NS server.yourdomain.com. @ IN A 127.0.0.1 * IN A 127.0.0.1 Someone memorably described this as killing an anthill one ant at a time.
RPZ
BIND also supports RPZ which can be used with publicly available blacklists (so you don't have to maintain your own lists)
Proxy
Some people feel a better solution is to use a HTTP-proxy such as Squid with Squidguard
SquidGuard is a URL redirector used to use blacklists with the proxy software Squid. There are two big advantages to squidguard: it is fast and it is free.
You can enforce the use of this by configuring rules in your router that only allow HTTP from the proxy server and disallow HTTP directly from any PC.