How to override an A record

[Bill Sandiford]

Hello!

I'm trying to solve a problem and I am looking for some assistance.

I want to configure my BIND 9 DNS server so that when one of my users tries 
to lookup a certain A record from an external domain the response they 
receive comes from my records for that particular record, but the rest of 
the domain will still resolve properly.  For example

Lets say I want to intercept all traffic to www.foo.bar.com at the DNS level 
to 2.3.4.5, but I want all other queries for bar.com and any other 
subdomains to work properly.  We also need to assume that transfers of the 
domain bar.com from its authoritive name servers are denied.

I need to know how to place a record for www.foo.bar.com into my DNS servers 
without breaking the lookups for all other records in that domain and any 
subdomains.

Any help would be much appreciated.

Regards,
Bill