Interactive PayPal payment page

I am a developer of software applications. My customers do not pay for my software. They can build product using the software, but must purchase a 'ticket' before that product is released. The software generates a job code. When they purchase a ticket for that job code, they are provided with a validation code. They enter that validation code into the software, and, if the validation code matches the job code, then their product is released. The request for a ticket and the provision of the validation code are currently handled through emails. I would like to automate that process through a web page on my existing domain. I would like a simple web page that has no links to other pages on the domain. That page will only be accessed by a direct HTTP address. The customer will be directed to the page by clicking a button in my software. The page will have a background image (provided by me) but no other links/components. When the user opens the page the only thing they will see is an input field, some text requesting that they enter their ten digit job code, and a button to 'continue'. Refer Image : Start.jpg. When the user clicks the 'continue' button, the webpage will validate that job code and will only proceed if the job code is valid (I will provide the algorithm for this validation). Encrypted in that job code will be the price. When the website validates the job code, it will also know the price for the ticket. If the job code is invalid, they get an error message and return to the start screen. Refer Image : Invalid.jpg. If the job code is valid, the page should show the payment amount and payment button. Refer Image : Valid.jpg. This will perform a PayPal payment for the amount that was defined by the job code. If the payment is not successful, the web page will show an error screen. Refer Image : Failed.jpg. If the payment was successful, a field containing a validation code for that job. The validation code is based on the job code (again, I will provide the algorithm). The validation code should be in a field that the user can copy so they can easily insert that code into my software. Refer Image : [login to view URL] I would like the developer to build the web page and help me install it on my domain. Following a bad experience with another freelancer who I contracted for a solution to this requirement. I would like the project in three stages with milestone payments at each stage. Stage 1 : The page is built and installed on your website where I can access it for review. Stage 2 : The page is installed on my website for final testing. Stage 3 : The page passes that final testing. Thank you for reading.