Your mediation agreement can be amended and the amended version signed by both parties can be filed with the court. The amendment would have the name of your case, case number, etc. and would just say, The mediation agreement dated ______ in the above-captioned case is amended as follows:  (Insert the changes).  At the bottom, it should be signed and dated by both parties. Changed circumstances such as a change in income would be grounds for a modification of child support.