Formula To Return A Result Based On A Set Of Criteria

I have an excel spreadsheet which has months of a year in a row increasing by one month in each respective cell. Under the row of dates are a row of numbers (Cash Flow for a project). The cells under each date start with negative amounts and then over a time turn positive.
Under this row there is another row which adds the above cells to give a running number.

In an unrelated cell I then ran a formula to work out the cumulative most negative number. I used a Min formula. What I am now looking to do is run another formula to work out which date was the lowest period in the calculation. I have tried a HLOOkUP but it never worked.

I have attached a spreadsheet would be grateful if you could asssit.

Thanks

Thanks worked perfectly.