Hopefully someone on this forum can help me. I've already posted this same question on other forums, but no luck yet.
( I have even included a sample of the spreadsheet for you to look at to see what I'm referring to... )

I have a column of values (E4:E87). I'm adding 1 value to this column manually each day...so tomorrow (July 24th) I will have E4:E88...and so forth. Each day is a new row.

In column Z (i.e. cell Z87) I have the formula =(SUM(O53:O87))/(SUM(E53:E87)). Z88 will have
=(SUM(somevalue:O88))/(SUM(somevalue:E88)). This gives me a resulting percentage for a rolling period of time.

I need an automated way to populate the "O53" and "E53" cell reference values ("somevalue") in the formula so that the SUM of the current row's cell (i.e. E88) through [a value earlier in time, above the current row] is 50 or greater. (The sum of the values should be as small as possible, but at least 50.)

The cells referenced by O53 & E53 should be different for each row...depending on how many rows it takes to have the value be at least 50.

On row 87, the sum of rows 87 thru 53 (column E) are needed for the value to equal or be greater than 50.
On row 86, the sum of rows 86 thru 53 (column E) are needed for the value to equal or be greater than 50.
However, On row 85, the sum of rows 85 thru 52 (column E) were needed for the value to equal or be greater than 50.

A sampling of the spreadsheet can be downloaded here:

https://dl.dropboxusercontent.com/u/18404362/NS%20Korp/Misc/Spreadsheet....

Thanks in advance for your help!

-rbtfinley