Hi all, i am trying to define a rare schedule,

consider the following example, say

loan amt is 16,000
say int is 12.00%
tenure is 12 months

the customer says that he will pay 4,000 at the end of the contract that is with the last installment, i defined the schedule as

P prin st date 1,000 M
I int st date M
P end date 4,000

now the system accepts this, but the monthly repay amount varies
that is P + I on every moonth varies,

without the last payment of 4,000 we use A annuity type which is core
which calculates equal payments

Term Balance Interes Principal Total
----------------------------------------------------------------------
12 16000.00 160.00 1274.44 1434.44
11 14725.56 147.26 1284.96 1432.22
10 13440.60 134.41 1295.57 1429.98
9 12145.02 138.79 1288.93 1427.72
8 10856.10 124.06 1303.66 1427.72
7 9552.44 109.17 1318.56 1427.72
6 8233.88 94.10 1333.63 1427.72
5 6900.25 78.86 1348.87 1427.72
4 5551.39 63.44 1364.28 1427.72
3 4187.11 47.85 1379.87 1427.72
2 2807.23 32.08 1395.64 1427.72
1 1411.59 16.13 1411.59 1427.72
0 0.00 0.0000

total int 1146.1470
total prin payed 16000.00


so how to tackle this...?
the balance should include the last payment of 4,000 every month, and at the last month it is 4,000 + final montly principal,

Term Balance Interes Principal Total
--------------------------------------------------------------
12 16000
.
.
.
.
.
5 B1 I1 P1 constant
4 B2 I2 P2 constant
3 B3 I3 P3 constant
2 B4 I4 P4 constant
1 B5 I5 P5 constant
0 4000 0.00

Where B1 to B5 are the balances which should be greater than 4000,
where P1 to P5 are the monthly principal payed

constant is I1 + P1,

after the last payment the balace should be 4,000