How to modify "A" records on the slave when master is down?

[stevehunter_1 at hotmail.com]

Hello.  I have two geographically different datacenters.  Each
datacenter has two instances of BIND.

There is one master out of these four.  The zones will have multiple
"A" records (pointing to the two datacenters to provide some minimal
amount of redundancy and load balancing)

What I want to do is put together a plan for when the master either
fails or the master becomes unavailable.

So if your master fails, or more likely, it becomes unavailable, and I
need to change the "A" records on the other slaves, how do you do it?

Can I have a master in each datacenter and a slave in each datacenter,
but a change made to any master propagates to all slaves?  For that
matter, can I just have four masters and be done with it?

It doesnt make sense that I could have multiple masters.. but I have
no idea how to solve this problem.  If datacenter A goes down for
three days, i want to be able to modify the slave "A" records to stop
pointing to the bad datacenter.  And when the datacenter comes back up
and the old master is alive, I want everything to work.