I must say that I agree with Sparklekitty. Ultimatums usually don't work for A's. I left my apt and told my AH that wasn't coming back until he checked into a therapy....well we (my 4 yr old son, 6mo daughter and I) were gone for 7 months until he finally checked in. You would think after a few weeks passed, maybe even a month or so he would've seen how serious I was. The problem was that he DID see how serious I was but HE WASN'T READY to get help, and that's what you have to be ready for. The saying goes...you lead a horse to water but you can't make him drink it. Hell, you can submerge the horse and he can drown on the water before he actually drinks it.
He's got to want it and don't be upset if your ultimatum isn't enough for him to "want it".