My husband went and filed his taxes alone with 2 of our 3 kids. He took the two that were in childcare and left the baby for me (she was home with me; no childcare). So I don't have any childcare expenses write-off at all. He left the home and took the money. Do I have a right to this? Can I get half of the money from the other two kids back? We did not agree about the kids.

Does he once again win? And I'm A$$ out as usual? What can I do?

It depends on a few things, did he pay for the child care? Are you still married? If not who has the kids? I am an accountant and would advise you to go talk to yours because he/she probably know the situation a little better as well as your state laws.

Also check what the court has decreed in your custody orders. That should have been taken care of already. Usually it has been customary for the courts to grant the deduction to the custodial parent so you really need to check. Also if he is filing as separate because your divorce is just getting started then you may be entitled to 1/2 the refund.
Taxes are noramlly from a previous years wages when you were / ( might have been ) married before filing for divorce.
Im not sure what stage your at but if you just filed this year then you need to check or at least ask your lawyer about it.

I am the one paying all day care expenses for all kids (last year and currently). We are still married. We are just separated. The divorce procedures has not started yet. The kids are currently back and forth between both of our homes.

Do I have any rights?

As far as the taxes goes your really going to need to get a copy of what exactly he filed because you have nothing in place at this time and its possible he filed his ( both of yours ) taxes illeagaly. So getting a copy is paramount. You should be filing with the status the tax code calls for. Your entitled to 1/2 the refund as he would be for you if you file separate returns. See answer above.