Calculating Loan Paydown

Hi!

I am trying to setup an excel spreadsheet to calculate paydown of a loan based on sale.

There is an initial outstanding balance. The balance needs to be adjusted when we have a sale. We will not know the sale price until the date of the sale, which means that input is adjustable.

What is the best way to setup a cell to calculate the following: (outstanding loan balance) - (sale price). Again - sale price is unknown so I need to know if there is a way to trigger the subtraction function using an IF formula, or something of that sort.

If you think you might know but need further clarification please contact me!

Thank you!

Thanks Shelton! That chart is great but not applicable to what I am doing.

Mine is simpler in regarding the pay down as there is no interest. The complicated part is setup.

Here's my example:
As of 5/1 the loan = $5000
On 5/23, a unit is sold for $1000 (out of 6 units)

I want the next cell to calculate the difference between the $5k and $1k, as a result of the $1k input triggering the math. Does that make sense?