Hello,
I'm ready to assist.
We will use PayPal IPN for your PayPal Business account.
Basically, once the number of words is converted into fee:
1. a form will be generated and posted to PayPal along with necessary data will be stored in database.
2. User make payment at PayPal and returned to thank you page.
3. In the background, PayPal will post some data to your server.
4. Upon receiving posted data from PayPal, your server will post back the data through socket to be verified by PayPal.
5. Then finally PayPal will post back the status of transaction.
6. Only if the status is VERIFIED and the payment is stated as COMPLETED, your server will mark the text status as "to be approved".
I hope the above mechanism will meet your requirements.
There is a note, since the transaction status and payment status were verified, you could skip the approval stage since we can make it as auto-approve.
Best regards.