I would create a sheet (copying the last) 30 or however many times you
wish. So a sheet for 2008, 2009 ... 2029, 2030. If however you are
just trying to get the final calculation then this isn't necessary I
just assumed that at the end of each year you wanted a review of the
year. Also your expenditure, interest rates, savings etc are all
variables that may change from year to year and this could then be
adjusted whilst keeping the history.

Hope the helps.