ccdB is the gene encoding the toxin. So any expression at all would be lethal. I think it highly unlikely you can do what you are proposing, at least not easily. It might be possible under a very tightly regulated promotoer, but I am even doubtful about that.
But what is it that you are trying to do, perhaps there are some other solutions that would work if you could provide more details.
Normally you have a strain with ccdA and then the plasmid for cloning carries ccdB, and not the way you are doing it.
One suggestion might be to have a plasmid that is temperature sensitive for replication carry the ccdA gene on it to make your competent cells. Then when you do your transformation you incubate your tranformation plates at 43oC. I'm not sure if that would work for you or not.