Here's one way you can manage it on your own. This is different than setting up an amortization payoff because it accommodates flexible repayment. If you'd prefer to adhere to a fixed monthly repayment of $111.25 or something, this is less useful. Otherwise...

Just add a line every month (I chose the 1st day of each month) and add a line every time there's a payment. That way you only enter the payments when made, and do nothing if no payment (except the monthly update on the 1st). If no payment is made, the balance just goes up.

You only enter data into the yellow cells. The white ones are formulae, that you copy down from the line above each time you add a line.

So Jan. 2 the loan started, effectively a negative 1000 payment.
Feb. 1 you update the balance.
Feb. 2 a payment is made, reducing the balance.
Mar. 1 you update the balance.
etc.

This is mildly imperfect because it rounds the interest to the penny, but it's essentially trivial. The interest method here is annual effective rate as stated, using i ^ (1/365) each day, also a trivial "imperfection."

You can still establish a scheduled monthly repayment amount with an amortization function such as PMT, but unless every payment is made on time, a flexible amortization approach such as below might work better for you.

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