How do you keep track of rental funds for capex and vacancy etc?

[John Fider]

Say you had 2 properties. Property 2 suddenly needed a new roof. How do you know if you've saved enough in cap ex funds to pay for it?   I can't imagine each property will have its own separate bank account. 

I guess I want it organized enough that I won't accidentally dip into another property's funds when I need to make upgrades, or if I had a vacancy, I know how much of the vacancy funds I've used up and avoid dipping into the Capex funds.

Do you use a program like spreadsheet?  Ideally I'd like one that's user friendly, one I won't need to make formulas for to make it easy to plug data in.