Multiple property payoff calculator

[Nathan Waters]

I know this was asked a while back but no one responded with anything. Does anyone have a calculator for multiple properties to calculate early payoff of multiple properties? I have 4 rentals and I'm actively pursuing more while I'm employed full time. I would like to have them free and clear when I quit my full time job and want to get a rough idea of how long that will take. I realize I can calculate them one by one, But I am a nerd for excel and hopefully someone has something out there. If not @Joshua Dorkin, maybe Bp can create a calculator like this in the portfolio tracker. Thanks and happy investing.

[Tim Stolt]

@Nathan Waters
I'm a bit of an excel need myself.  Unless you are wanting something super flashy,  I'm thinking a payoff calculator could be fairly easy to build across several worksheets, just copying a new sheet whenever you add a new property. 
Start with an input sheet that feeds amortization schedule sheets and your net income calculator. The hardest thing to build in would be exess payments snowballing, but not impossible. As with any workbook, write one equation at a time until the puzzle is complete. Good luck.