Paying for items via point system

Hi, I am new to this forum and would like to ask a question about coding a point based payment system.

By this I mean a way in which users can have a balance of digital money on there account, and with that use it to buy things (using digital currency).

The way in which users gain digital currency is by being rewarded it, or trading it (buying it) using another currency from the store. I don't want to discuss how they would be rewarded, or buying the currency, but how could I give users an option to pay through digital currency and have a balance of digital currency tied to there account.

I know how to code in php, and have already worked with modifying phpbb (os forum) and wordpress (os blog), but does anybody have any information relative to this, or useful code snippets?

I'm actually implimenting this in a big project I'm currently working on. It wasn't too hard to do. I just added a field to the 'customer' table called 'points'. Then wherever I want points added or subtracted, I just call on a custom model function to adjust the points in the DB.

does anybody have any information relative to this, or useful code snippets?

I don't belive anyone has created a module for this. I don't think it could be done as a contribution easily because it would be so custom and specific.

I understand how you could keep a record of points and add/subtract, but I am not sure how you would implement adding/subtracting points, relevant to a user purchasing an item, or using the points as the only factor of paying for something.

Is there any specific part/page of code I could edit to use this?

I plan to have that part of my project done by the end of this week, so I'll let you know what I come up with .