Total Amount Donated in Postbit based on Subscriptions

[manofphat]

Hello,

I'm looking for code that will take how much money a user has spent in the paid subscriptions section and put it in a custom field that I can implement into my postbit.

Lets say that someone had already subscribed for something that was $15 and they just renewed their subscription, the field would now say $30.

I figure it might be something simple?

Thanks!