Failure detection to change A records

Hi,

I played with round-robin and this is working fine. But this does not
fit with our need of failure detection.
I'm looking for a way to test some services availaibility of some
hosts, to enable or disable A records.

For example, I set up two ldap servers in our network.
On our DNS I run some knid of ldap watchdog, and when a ldap server
fails, the watchdog removes the A record for ldap.mycompany.com

What is possible with bind ?

--
Nicolas Ecarnot