There are forms on the site to modify child support at http://courts.in.gov/selfservice/2333.htm.
Whenever the court considers the issue of support, it takes into consideration all of the relevant information of both parents to calculate the appropriate amount of support. Even if one parent gets an increase in income or loses a job, the court has to look at the income position of both parents, and there may not be an automatic reduction or increase in support. When support is modified, both parties should be prepared that the support could go up or down.
All of Indiana Code 31-16 at http://iga.in.gov/ is devoted to establishing and collecting support. You should review this code section and all related sections dealing with support to better understand what laws apply.Before making the decision to represent yourself in court, please review the information and videos at http://courts.in.gov/selfservice/2361.htm to determine if self-representation is right for you, find more information about the court process, and see what will be expected of you if you choose to go to court without an attorney.