HELP need Formula
 

I am trying to set up my yearly expences in a work sheet for debt
consoladation. I have some debts that will be paid in 16 months some like my
mortage that will be a number like 330 months. I need the formula that will
tell me my yearly expences untill all paid off. EX. 1st 16 months my debt
will be the same but once i reach my 17th month i will be done with one of
them so my monthly expences will drop thus effecting my annual spendings.
I've already designed a worksheet showing all my creditors, monthly payments,
total balance, and even use a formula to find out how many more months till
paid in full. But can't figure out how to factor in percentages(APR) and
design a cell that will do the math for a yearly over view. hope I explained
that correctly. Just incase 1st year i'll spend $22,879 but the second will
drop to $19,945 do to the elimanation of some of my charge accounts.