What file contains this function?

I want to add a function that will run only when a user has purchased a membership upgrade. That is when the member pays for the upgrade, the site gets the success payment info back from the IPN, my function will insert some additional info into a custom database table. I would imagine that I could put this function in with the function that is built in somewhere that tells the site to update the user's membership level in the database when payment has been successful. The problem is, I can't find this. Does anyone know what file contains the code to update the member's membership level upon successful payment for the upgrade?

Thank you.

I Have good module that can help you! - http://www.boonex.com/unity/extensions/entry/Credits_system
for example : http://www.avlija.net/

Thanks SashaE, I have sent you a PM about this. It looks like a good mod but it doesn't seem to be what I need to accomplish in this case. Basically, what I am looking to do is to have a user's username and password inserted into the member database of a seperate script using the same database as my Dolphin install. I can have this happen easily when the user joins by putting the function into the profilecontroller file, however, I don't want to do it when they join, I want it to happen only when they have paid to upgrade to a membership level. That is, paying for the upgraded membership not only gives you more access in Dolphin but makes you a member of another area of my site.

You should be able to place your code in the function setMembership in inc/membership_levels.inc.php

By placing it there, it should work if they purchace, or you as admin manually upgrade them to that level thus covering both possibilities.

Passed to that function when it's called is the membership id. So you should be able to insert some code in that function to do your inserts if the passed membership id matches the membership id of the membership level you want to match to.

You should even be able to add code there to remove the id from your custom table if they should down grade their membership.

Many thanks Deano! I will take a look there.