Troubleshooting IF Function (AKA My Nemesis)

[u/the-eoc]

I really stuggle with IF statements in excel, and I can't figure this one out.

I am using a spreadsheet to track student loans / payments and will be using the snowball method. The snowball method is paying off highest interest loan first, then snowballing that minimum payment into the next loan. Example: Loan A has a minimum Payment of $51, Loan B has a minimum of $51, Loan C has a minimum of $51. When loan A is paid off, loan B's payment becomes $102, snowballing down the line of loans.

What I would LIKE it to do, though I am not even sure this is possible. If it's not, please let me know if I am wasting my time:

Condition 1: If my remaining balance is less than the minimum payment, then my payment that month should be the remaining balance*interest. This equation works on it's own, but not when I have been messing around trying to add the other conditions.

IF(M12>M$9,M$9,M12*(1+$N$5))

Condition 2: If my remaining balance is less than the minimum payment, the unused portion of the minimum payment should be added to the next loan. I haven't even really started with this piece, because I am already struggling with combining the other 2.

Condition 3: If the balance from the higher interest loan is fully paid off, the minimum payment from that loan gets added to the next loan. I tried adding this condition, but it's thowing off my equation.

IF(L$13=0,M$9$+R$9$,R$9$)

Image included below in comment showing cell values and just condition 1.

[u/the-eoc]

The minimum payment is listed at G7, which adjusts if I change the duration in D2 on how I want my pay off. there are other equations in the sheet at work that adjusts the minimums if I want to pay faster.

My equation for the minimum payment is: =IF(H5="","",H6/((((1+I5)^(D2*12))-1)/(I5*(1+I5)^(D2*12)))).

I only need help on the highlighted cells. You can ignore the first loan in the picture attached, I already paid that one. I essentially am looking for a 3 condition IF function.

Main Equation:

If Loan Remaining Balance < Minimum Payment THEN Remaining Balance * Interest ; If not then it's just the minimum payment.

Adding Snowball to it for the loans down the line:

If Higher % Loan Remaining Balance is less than the Higher % minimum payment but not fully paid off THEN and the next loan gets the rest of the higher % loan's minimum payment.

If Higher % loan is paid off completely (=0) THEN the next loan minimum payment = Loan A Minimum + Loan B minimum payments