Unique Loan Repayment calculation

[MegaD]

Hi

I am an absolute novice with Excel (only used templates, mostly...) so please excuse if there is a simple answer to my issue which I have overlooked.

I am borrowing $2500 from a friend. I will be repaying different amounts at different times. We have agreed that I will repay the $2500 plus the interest she would have earned from her savings account on the amount loaned, 1.5% annually (which may change if rates improve before I have fully repaid her) calculated daily and paid monthly.

She is loaning me the money to help me purchase equipment needed to start a small business (a new camera for my photography business), I will be paying her back with any profit I earn until I have repaid the amount including the interest.

I am not sure if I am overthinking the situation and all it is is a simple interest calculation or if this is a more complicated issue. I am looking for a way to be able to input the amounts I have repaid and calculate the interest on the amount still outstanding until I reach a zero balance owed.

I think it's simply a FV calculation in which I would change the PV each time I make a payment, but I am not sure and would love some experienced feedback.

Any help or guidance in figuring this out is MUCH MUCH appreciated!!!