Building a web based pension calculator

Hi there

This is my first posting, so apologies if this is not the correct board or not a question members would respond to normally.

We are currently trying to put together a web based pension calculator and am unsure about how to go about trying to put the equation together for our programmers to begin building it.

The calculator itself is meant as an estimate only to give people an idea of how much they may need/how much of a shortfall they may have.

The calculator will take into consideration:

-current age

- age of retirement

-current salary

-existing fund

-target income in retirement per year/per annum

-the ability to escalate contributions by the rate of inflation assuming that this is 2.5%

- the ability to change the percentage of tax free cash

- personal contributions, per month

-the ability to delay starting your pension by a number of years

with the hope to get an example of

- total pension fund

-tax free amount

-projected income and percentage of target income

-preojected income and percentage of target income if you delay by x years.

Any help would be very much appreciated, even a point in the right direction!

Many Thanks in advance