Go to File... New... General Templates... Spreadsheet Solutions... "Loan
Amortization"
if you need the actual formula to calculate interest...
Principal = Payment * ((1-(1/((1+r)^(n*y))))/r)
Where:
n = number of periods per year
y = total years
r = interest rate per period, given by this formula:
r = Annual interest rate/n
Payment = (Principal * r)/(1-(1/((1+r)^n*y))
HTH
Die_Another_Day