One way is: you need a way to store the info e.g:
class Payment
{
string month;
float amount;
}
them a collection such
List<payment>
to hold the data and add to Listbox etc.
you can make an enum or array with names of the month, then
float remainder=10000;
int startMonth=1;
int numPayments=(int)remainder/12;
float installment=remainder/numPayments;
for(int i=0; i<numpayments;>{
}