This is a common question. The answer is to look at your Marital Settlement Agreement and the Findings of Fact and Conclusions of law. It will say in those documents. If it does not say you have to pay for half of those kinds of things or that he has to ask your permission first, then you do not have to pay.
It has to specifically say you have to pay whether or not you agree (that is not likely). It is far more likely to say you must agree, or it will say nothing at all. Unless the MSA or JOD states variable costs are 50/50 without approval or agreement, YOU DO NOT HAVE TO PAY.
Talk to an attorney on a free consultation. Take your MSA and JOD with you and any other orders you have had since then.