We affirm the orders under review except that portion of the order rendered on July 14, 1997, by which the effective date of the reduction in child support was made retroactive to March 1, 1996. We reverse only that portion of the July 14, 1997, order, and we remand this case to the trial court for the effective date of the reduction to be set at April 3, 1997, the earliest date that the issue as to a reduction in child support could have been determined to have been tried by consent.