Temporary Change in repayment Schedule of 55A

Dear Expert

i have the below issue.. i create a loan using 55A.. I defined installment plan has been entered in the instrument structure .. but if i have installment amount 100000 $ in March , which i made an agreement with bank to divide this installment on two months 50k in march and same in April.. how can i reflect this in the instrument since this deal will happen this time only and the rest of installment will be one same original dates..

Regards

Mahmoud El nady