Enrolment

Except that if the course cost is updated, your numbers are all wrong -> Exactly, as I mentioned in the "extraneous" part. That and the fact that if a user enrolls in a course twice before the accounting program is run (say a 2 day course),
It can probably be a nice extension to the current PayPal plugin are you thinking of writing it so that it can be included in the official release?>
Eh, if I get anyone asking me to. I'm not the prettiest coder and I haven't even read moodle's coding policies. I tend to make my own connections to the database instead of using moodle predefined database functions. Its also not the biggest thing for me in regards to editing moodle right now.
I am going to try to add a point system to my site, based on various things such as volunteering, in which teachers get a monthly allotted amount of points to give out to students (reset at the end of the month) - the points go towards enrolling in courses that have a cost... There are various other dynamics but back to the paypal thing.
I took a brief look at the paypal enrollment in the process of writing this response and I found: Pretty simply, paypal sends the paypal/ipn.php file a confirmation key, moodle sends it back, paypal responds, moodle reads the response, checks the response against predefined problems, database inconsistencies (in price). Moodle then uses its universal insert_record function with the data object from the paypal info. There is already an attribute within the object on how much was spent. In fact, moodle does a check to make sure that the price spent was the price necessary to enroll:

 145 if ($data->payment_gross < $cost) {
 146 email_paypal_error_to_admin("Amount paid is not enough ($data->payment_gross < $cost))", $data);
 147 die;
 148  149 }

So, there is a really easy way to get the payment information, and it doesn't require me spending time being a do-gooder (apart from writing this). If I am correct about the nature of the insert_record function, it basically takes an object and fills whatever fields in finds in the table named. As such, the only thing needed to get information on the payment amount is to add the field "payment_gross" to the "enrol_paypal" table. Hah, and I thought I was going to have to deal with paypal!... oh wait, that's that ecommerce solution I'm using, doh. Anyway, I think that is the solution but if I am wrong, you can tell me or I will find out when I try it.