I am currently working on a site for a client that offers proof writing services and need some help with the checkout system.
The ideal system would work like this:
The user fills out a form with information about the paper (format, structure, etc.). The user then copy and pastes their paper into a textarea that counts the number of words and displays a total in a read-only input box below. Everything up to this point is definitely doable. Where I'm running into trouble is having the calculation then affect the total price of the service (charging by word, depending on the number of days selected until the paper is due). Again, I can write a script to do all this and calculate the total price, but I don't know how to send the form information to the database and then enter the total price into a custom Paypal field in order to use Paypal to charge the user.
I have thought about doing this a few different ways but am open to suggestions. One is to accept the user information on one screen and after submitting it to the database, having a second screen that imports the word count price calculation into the Paypal custom field.
Another idea (ideally) would be to send the form to two places, both the database as well as to Paypal so that it would take less clicks for a user to submit and purchase the service.
Another idea I had was to use an altered shopping cart plugin like WP-Ecommerce and create some kind of custom field that would help in calculating all of this, but unfortunately, try as I might, I haven't been able to figure out how to make it work as it should.
Any help or ideas would be greatly appreciated. I have limited PHP knowledge and need any solutions like this spelled out for me. Let me know if any more information is needed or if I'm not clear about what needs to happen. Thanks in advance!