I am working in excel 2003 where my data is like:

1-jul 2- jul 3-jul 4-jul total credit bal by days
0.9 0.1 0.4 0.5 1.9 1.1 0.8 xx

In place of xx above, I need a formula where it should look from 4-jul to
1-jul and give number of days from when bal is due. In above example answer
sholud be 2 as bal 0.8 falls within sum of 4-jul + 3-jul.

Need help from experts.
--
Alisaheb