Mysql Failover with Slave Database and Replication?

[Make Money?]

Here's what I'm trying to do:

I want to use Vbulletin's slave database option AND have failover. I've got 2 servers. I'm using www.zoneedit.com to round-robin my dns between Server A and Server B. Both Servers Vbulletin's are writing to the database on Server A and reading from the database on Server B.

In the event Server A fails, Server B needs to suddenly now both read and write to it's own (hopefully up-to-date) replicated database. Is there any way to tell Server B it needs to now stand on it's own 2...erm...legs?

Then what happens when Server A recovers and comes back online? While the servers can each be configured to act as both master and slave, Server A may not have caught up before it is thrust back into action. Perhaps there is a way to force Server A not to appear? You can specify a string on a page for Zoneedit to check to see if a server is offline or not. Maybe a script in vbulletin which checks the binlogs of both servers to see if they're caught up before revealling some text?

And maybe this script could even appear/disappear depending on the load of the server, that way Zoneedit would switch the dns long before the actual crash occurs!