Interest Calculator difficulty, date variables, etc...

[dreinisch]

I having a lot of difficulty in creating my own excel calculator that will solve for cell G4 (Unpaid Principal Balance at the date of sale) which is the end result I need. The variables that are taken into consideration range from cells D3 through D13. So, if a $500,000.00 loan was amotorized over 40 years, had an initial rate of 6% and the first payment date was 12/1/2000…..the result would be simple. However, with a twist thrown in there where the rate was reduced from 6% to 4% from 5/15/2002 through 5/15/2003, that would change things. Then….payments stopped for whatever reason on 8/1/2009 and the property was later sold on 10/15/2011.

Cell D3 needs to be able to be modified. So the use may enter in any dollar amount.
Cell D4 needs to be able to be modified. So the use may enter in term.
Cell D5 needs to be able to be modified. So the use may enter in any rate.
Cell D7 needs to be able to be modified. So the use may enter in any date.
Cell D9 needs to be able to be modified. So the use may enter in any date.
Cell D11 needs to be able to be modified. So the use may enter in any date.
Cell D13 needs to be able to be modified. So the use may enter in any date.
Cell G3 needs to be able to be modified. So the use may enter in any date.