PHP/Wordpress developer required to write small piece of code

I need a web developer that knows how to code in PHP and uses WordPress. I want a small piece of code which can be inserted into a program in order to provide the necessary functionality.

BACKGROUND
I have a basic home insurance website, which provides a dummy quote. The customer enters their details and then selects how much their current annual or monthly premium is and enters the amount.

The customer then clicks the "GET QUOTE" button. Once the user clicks get quote a new screen is displayed on which the quote amount is shown.

On the click of "GET QUOTE" I want the following to occur:

SCENARIO 1
If the customer selects Current Price PER MONTH and enters an amount, carry out the following validation:
If the amount is less than £6.06 then display "N/A"
If the amount is greater than or equal to £6.06 then carry out the following:
Randomly select a number between £0.11 and £1.05 and then minus it from the original amount the customer entered. Display this amount on the screen.

SCENARIO 2:
If the customer selects Current Price PER YEAR and enters an amount, carry out the following validation:
If the amount is less than £72.61 then display "N/A"
If the amount is greater than or equal to £72.61 then carry out the following:
Randomly select a number between £1.21 and £12.60 and then minus it from the original amount the customer entered. Display this amount on the screen.

FINALLY
If the customer clicks the GETQUOTE button between 8.00pm and 8.00am MON to FRI or FRI 8.00pm to MON 8.00am, they need to be redirected to a different page

Details of the code and server will be provided once a bid is accepted.
DEADLINE – Saturday 29th January 2011