We are working on a student late payment balance payment agreement form and cannot get the calculations to work. I can't find a place where it teaches us where to use what kind of formula's that are specific to this. We have a table set up with three fields and on the Columns Advanced area we have this formula on the Balance.

=SUB(Total_Unpaid_Balance_Outstanding, Payment_Plan_for_Outstanding_Balance.Payment_Amount)

But it's not actually calculating, it states there is a calculation error. All of the formula's we've found have a least one static number in them, not two variables that need to add and/or subtract. When we insert static numbers instead of variables the calculations tend to work. Is there a better formula for getting a calculation with variables?

Side Note: Each of the fields that are variables are Single Line fill in as each students numbers are different, drop down etc would not work because of this.

We have a form very similar we are working on for another program but it's multiplication and we are running into the same issue.

Thank you for your help!