Try the NPER function. NPER returns the number of periods for an investment based on periodic, constant payments and a constant interest rate. Input the pv (your current savings) and pmt (annual contributions) as negative numbers and fv (your savings goal) as a positive number and rate (your expected earnings rate per year) and it will return the number of years needed to reach your goal.
If something cannot endure laughter.... it cannot endure.
Patience is the art of concealing your impatience.