The Excel CUMPRINC function calculates the cumulative payment on the principal of a loan or investment, between two specified periods.
The syntax of the function is:
Where the arguments are as follows:
rate    The interest rate, per period. 
nper    The number of periods over which the loan or investment is to be paid. 
pv    The present value of the loan/investment. 
start_period    The number of the first period over which the payment of the principal is to be calculated (must be an integer between 1 and nper). 
end_period    The number of the last period over which the payment of the principal is to be calculated (must be an integer between 1 and nper). 
type    An integer (equal to 0 or 1) that specifies whether the payment is made at the start or the end of the period: 0  the payment is made at the end of the period; 
Cash Flow Sign Convention:
Note that, in line with the general cash flow sign convention, cash outflows are represented by negative numbers and cash inflows are represented by positive numbers. This is seen in the example below.The following spreadsheet shows the Excel Cumprinc function used to calculate the cumulative payment on the principal, during each year of a loan of $50,000 which is to be paid off over 5 years. Interest is charged at a rate of 5% per year and the payment to the loan is to be made at the end of each month.
Formulas:
 Results:

Note that in this example:
For further details and examples of the Excel Cumprinc function, see the Microsoft Office website.
If you get an error from the Excel Cumprinc function, this is likely to be one of the following:
#NUM!    Occurs if either:

#VALUE!    Occurs if any of the supplied arguments are not recognised as numeric values. 
Also, the following problem is encountered by some users:
The result from the Excel Cumprinc function is much higher or much lower than expected.
When calculating monthly or quarterly payments, many users forget to convert annual interest rates or the number of periods to months or quarters.
Solve this problem by ensuring that the rate and the nper arguments are expressed in the correct units. I.e.:
months = 12 * years quarters = 4 * years  monthly rate = annual rate / 12 quarterly rate = annual rate / 4 