I need a comprehensive mortgage calculator

I need someone who specialises in Excel or similar program to create a fully comprehensive mortgage payment, repayment, overpayment, and equity share calculator.

It should include an option for provision for a fixed rate part of the term, if applicable to the mortgage. The fixed rate is usually between 2 - 5 years depending on lender, after which the product reverts to a variable rate as notified by the lender. The finished product should be fully comprehensive in meeting our needs, and contractors are welcome to suggest further enhancements for the project we may not have considered or be unaware of.

The calculator should show the contributions of two parties to the mortgage, and a calculation of their precise equity share in the property as a result, as the contributions will likely be unequal over the course of the mortgage term. It should also include the parties' respective deposit contributions.

It should also show the mortgage information overview, balance at a specified year, running summary, and breakdown of any extra contributions, overpayments, or underpayments by each contributing party.

A breakdown of payments should also be useful showing payment number, date of payment, interest rate, interest due, payment due, extra payment made (broken down showing each parties' contribution), capital paid, and balance remaining on the mortgage as a result. A graph showing balance, any extra payments, and the interest rate history would be useful.

Though we are not intending to incur Early Repayment Charges (usually due during the fixed rate part of the term), to cover all possibilities it would be useful for the calculator to show how this will change the total balance due for redemption of the mortgage. Though we are planning to pay off other ancillary fees at the start of the mortgage, such as the product fee and other small fees added to the balance, to ensure the calculator is comprehensive this may be useful to include, though we look forward to hearing any contractor's comments.

Provision for remortgaging during the term and carrying over equity shares held would also be very useful.

Though we are intending to take a repayment mortgage, ability to provide an interest only calculator to this spec is desirable.

A home affordability calculator would also be useful but not essential.

Though I found the calculators at Vertex 42 interesting, none seemed a fully comprehensive 'all in one' option, and none had provision for the fixed rate part of the mortgage term as is common in UK mortgages.

The currency should be in pounds sterling.

We look forward to hearing from you.

Thank you.