Partially amortized monthly debt schedule

[fkhan123]

Dear All,
Hope you are well.

I am struggling with a problem and need your help.

I am preparing a monthly debt payments schedule in which there is additional debt raised each month. Also, only part of the debt is amortized and remaining is interest only

Below is sample data:

			12/31/2022​	1/31/2023​	2/28/2023​	3/31/2023​	4/30/2023​	5/31/2023​	6/30/2023​	7/31/2023​	8/31/2023​	9/30/2023​	10/31/2023​	11/30/2023​	12/31/2023​
	Cumulative Debt		10,725,819	21,837,602	42,771,934	157,048,425	580,866,699	1,245,975,469	1,669,793,743	1,784,070,234	1,805,004,566	1,816,116,349	1,826,842,168	1,837,562,245	1,848,282,290
	Monthly Amount Service
	Amount		10,725,819	11,111,783	20,934,332	114,276,491	423,818,274	665,108,770	423,818,274	114,276,491	20,934,332	11,111,783	10,725,819	10,720,077	10,720,045
40%​	Amortized		4,290,327	4,444,713	8,373,733	45,710,597	169,527,309	266,043,508	169,527,309	45,710,597	8,373,733	4,444,713	4,290,327	4,288,031	4,288,018
60%​	Interest Only		6,435,491	6,667,070	12,560,599	68,565,895	254,290,964	399,065,262	254,290,964	68,565,895	12,560,599	6,667,070	6,435,491	6,432,046	6,432,027
15​	Term
12​	Payments Per Year
4.00%​	Rate
	Debt Service
	Opening Balance
	Principal Payment
	Interest
	Closing Balance

I am unable to come-up with the right formula for this, any suggestions will be very helpful.

Please let me know if possible.

Thank you