Failure to exercise time-sharing results in an adjustment of child support. “We previously held that application of section 61.30(11(b) is mandatory. Seiberlich v. Wolf, 859 So. 2d 570, 571 (Fla. 5th DCA 2003). Florida law mandates a reduction in child support whenever the non-custodial parent spends a “substantial amount of time” with the child. § 61.3O(1)(a), Fla. Stat. (2006). It seems intuitive that, conversely, the failure to spend time with a child mandates forfeiture of the right to a reduction in child support. The Legislature has specifically provided that a parent’s failure to exercise court-ordered or agreed-upon time-sharing, not caused by the other parent, resulting in the adjustment of child support “shall be deemed a substantial change of circumstances….” § 61.30(11)(c), Fla. Stat. (2001). That modification is “retroactive to the date the noncustodial parent first failed to regularly exercise court-ordered or agreed visitation. Id.” Buhler v. Buhler