husband refusing to accept cost certificate

This post a bit on a different spectrum but still related and any guidance would be greatly appreciated.
I have managed to get CAO in my favour and the judge saw the repetitive harassing behaviour of my husband, a cost order was passed for him to bear the cost of legal proceedings, but since my husband is abroad, he refuses to follow it.
I have got no child maintenance for last 6 years and spent significant amount on this CAO case.
Anyone experience this? what are my options?

An order for costs needs to be quantified if there is no 'number' on it.

There are some costs order which say "pay £x amount" which makes it easy to enforce but most orders say "costs to be assessed if not agreed" which means there are a number of hoops to ump through.

This is made more problematic as your ex is in a different country which means service of documents might be a problem but enforcing a money judgement could be impossible.

You need to find out what your prospects of recovery of monies are before you embark upon quantifying what your costs are.

Charles