I'm not sure what the details of your situation are, but DH's child support is through the county his ex USED TO live in.
In Florida, divorce and child support proceedings must go through the county that the RESPONDENT lives in. Therefore, since DH filed, he had to file in the county his ex lived in. Even though she has since moved to a different county, the child support is still through that county. We attempted to change it because this particular county is a royal pain, but that would have been a whole other rigamarole and I believe she had to agree to it. I assume that even if she moved out of state, that wouldn't change where the child support case was held - unless someone petitioned to change it.