Formula to return date if cumulative amount meets criteria

[jumbledore]

I have 2 columns for dates and amounts paid
I want a formula which will determine the date when the cumulative of the amounts just exceeds or equals a given value. So suppose I have the following:

Dates Amt
16-Jul-14 10000
1-Aug-14 4567
3-Aug-14 3000
Now suppose I have 14,000 as my "cut-off" amount. I want a formula which should return the date, 1-Aug-14 as the cumulative amount until 1-Aug is 14,567 which is just above the cutoff of 14,000. The formula should not return 3-Aug-14 even though it meets the criteria.
Thanks

 

[jumbledore]

I just found out, it seems the column headers have to correspond exactly to the ranges used in the formula. For example the amounts column should be in column D, name in C and dates in D, else the formula doesn't work