Debt Snowball Calculation? Is there one?

[SirEvan]

I'm trying to learn Java and Android development, and at the same time maybe try and earn a few $ doing so. One of the apps that I bought a while back was a debt tracking app that helped you keep track of your debt, with the option of using a snowball method to continue piling your individual payments on towards the next debt. This program was severely lacking in features though, and as a first app I wanted to try and tackle making a better mousetrap...or debt trap I suppose.

I'm not a financial expert, nor a finance major, so I'm not too keen on finance formulas, and methods, but I've seen excel workbooks that have macros to help show debtsnowball methods. Does anyone know if there is some kind of mathematical formula behind debt snowballs or avalanches that I can code for? even if it's a for loop or if/ else if block, I'm trying to understand how best to add this feature to the app, short of trying to disassemble the other one and see how it was done there..

So tell me...is there some sort of formula that can be applied to solve this? Or am I going to have to do it the hard way by tracking how many months are left for each debt, then applying remainder to next debt, etc...?

Thanks