You could choose to have your child support handled through the local Child Support Services, an off branch of the District Attorney's office. They will basically take over control of the whole child support situation including having the payments sent to them, and then they send you a check. They will handle all the legal matters for you including support reviews every couple years or when there is a substantial change in finances, usually 25% change is considered substantial, that falls inside the 2 year schedule.
You could even attempt to do it yourself, I mean you are allowed to and it's really pretty cut and dry as their is generally some sort of state guidelines to figure support according to income. Here's a couple Texas links that you could check out.
http://www.child-support-collections.com/support-laws/t...ild-support-law.html
http://www.alllaw.com/calculators/Childsupport/texas/