20-108.2(D)  Except for good cause shown or the agreement of the parties, in addition to any other child support obligations established pursuant to this section, any child support order shall provide that the parents pay in proportion to their gross incomes, as used for calculating the monthly support obligation, any reasonable and necessary unreimbursed medical or dental expenses that are in excess of $250 for any calendar year for each child who is the subject of the obligation. The method of payment of those expenses shall be contained in the support order. Each parent shall pay his respective share of expenses as those expenses are incurred. Any amount paid under this subsection shall not be adjusted by, nor added to, the child support calculated in accordance with subsection G. For the purposes of this section, medical or dental expenses shall include but not be limited to eyeglasses, prescription medication, prosthetics, orthodontics, and mental health or developmental disabilities services, including but not limited to services provided by a social worker, psychologist, psychiatrist, counselor, or therapist.