Price changing code/script for website

I am looking to have an html code/script written up to add onto my website, I need it to do the following: - Have a starting price - As time goes on, the price needs to automatically go up at certain intervals until it reaches the final price for example: - set the starting price at $5, then at every 2 minutes, the price displayed needs to be automatically updated with a $1 increase, until it reaches the final price of $10 I need to be able to set these factors myself, I need to be able to change the following: - starting price - price increase time interval - price increase amount per interval - final price to stop at I will need this to have a "buy now" button attached to allow the user to buy the item at the price visible. Ideally should be integrated with PayPal for payment or if it is easier, when the buyer presses buy-now, they are taken elsewhere where the price selected is secured and then they can proceed with payment. I have seen several of these programs written before and used all around the internet so I do not expect the cost of the job to be high. Thank you